In July, President Obama met for 45 minutes with leaders of American Jewish organizations. All presidents meet with Israel’s advocates. Obama, however, had taken his time, and powerhouse figures of the Jewish community were grumbling; Obama’s coolness seemed to be of a piece with his willingness to publicly pressure Israel to freeze the growth of its settlements and with what was deemed his excessive solicitude toward the plight of the Palestinians. During the July meeting, held in the Roosevelt Room, Malcolm Hoenlein, executive vice chairman of the Conference of Presidents of Major American Jewish Organizations, told Obama that “public disharmony between Israel and the U.S. is beneficial to neither” and that differences “should be dealt with directly by the parties.” The president, according to Hoenlein, leaned back in his chair and said: “I disagree. We had eight years of no daylight” — between George W. Bush and successive Israeli governments — “and no progress.”

It is safe to say that at least one participant in the meeting enjoyed this exchange immensely: Jeremy Ben-Ami, the founder and executive director of J Street, a year-old lobbying group with progressive views on Israel. Some of the mainstream groups vehemently protested the White House decision to invite J Street, which they regard as a marginal organization located well beyond the consensus that they themselves seek to enforce. But J Street shares the Obama administration’s agenda, and the invitation stayed. Ben-Ami didn’t say a word at the meeting — he is aware of J Street’s neophyte status — but afterward he was quoted extensively in the press, which vexed the mainstream groups all over again. J Street does not accept the “public harmony” rule any more than Obama does. In a conversation a month before the White House session, Ben-Ami explained to me: “We’re trying to redefine what it means to be pro-Israel. You don’t have to be noncritical. You don’t have to adopt the party line. It’s not, ‘Israel, right or wrong.’ ”

There appears to be an appetite for J Street’s approach. Over the last year, J Street’s budget has doubled, to $3 million; its lobbying staff is doubling as well, to six. That still makes it tiny compared with the American Israel Public Affairs Committee, or Aipac, whose lobbying prowess is a matter of Washington legend. J Street is still as much an Internet presence, launching volleys of e-mail messages from the netroots, as it is a shoe-leather operation. But it has arrived at a propitious moment, for President Obama, unlike his predecessors, decided to push hard for a Mideast peace settlement from the very outset of his tenure. He appointed George Mitchell as his negotiator, and Mitchell has tried to wring painful concessions from Israel, the Palestinians and the Arab states. In the case of Israel, this means freezing settlements and accepting a two-state solution. Obama needs the political space at home to make that case; he needs Congress to resist Prime Minister Benjamin Netanyahu’s appeals for it to blunt presidential demands. On these issues, which pose a difficult quandary for the mainstream groups, J Street knows exactly where it stands. “Our No. 1 agenda item,” Ben-Ami said to me, “is to do whatever we can in Congress to act as the president’s blocking back.”

The idea that there is an “Israel lobby,” with its undertones of dual loyalty, is a controversial notion. It has been around since the early 1970s at least, but it became a topic of wide discussion only after the publication of a notorious article in The London Review of Books in 2006 by the political scientists John Mearsheimer and Stephen Walt. The article, which was expanded into a book, infuriated many readers by its air of conspiratorial hugger-mugger; by its insistence that Jewish neoconservatives had persuaded President Bush to go to war in Iraq in order to protect Israel; and by the authors’ apparent ignorance of the deep sense of identification many Americans — Jewish and gentile — feel toward Israel. But the authors made one claim that struck many knowledgeable people as very close to the mark: The Israel lobby had succeeded in ruling almost any criticism of Israel out of bounds, especially in Congress.

“The bottom line,” Mearsheimer and Walt wrote, “is that Aipac, a de facto agent for a foreign government, has a stranglehold on Congress, with the result that U.S. policy is not debated there, even though that policy has important consequences for the entire world.” Mearsheimer and Walt also wrote that Aipac and other groups succeeded in installing officials who were deemed “pro-Israel” into senior positions. This is, of course, what effective lobbies do. The Cuba lobby, for example, long operated in the same way. But Israel is a much more important American national-security interest than Cuba. No country, whether Israel or Cuba, has identical interests to those of the United States. And yet mainstream American Jewish groups had implicitly agreed to subordinate their own views to those of the government in Jerusalem. The watchword, says J. J. Goldberg, editorial director of The Forward, the Jewish weekly, was, “We stick with Israel regardless of our own judgment.”

American Jewish voters are overwhelmingly liberal and Democratic, but as Jewish groups moved to the right along with Israel in the 1980s, the groups increasingly made common cause with the Republican Party, which from the time of Ronald Reagan was seen as more staunchly pro-Israel than were the Democrats. Jewish groups also began to work with the evangelicals who formed the Republican base and tended to be fervidly pro-Israel. Indeed, when I met with Malcolm Hoenlein in July, he had just come from a huge Washington rally sponsored by Christians United for Israel, whose founder, the Rev. John Hagee, has denounced Catholicism, Islam and homosexuality in such violent terms that John McCain felt compelled eventually to reject his endorsement during the 2008 presidential campaign.

George W. Bush shared the views of the mainstream groups on Israel and Palestine, on Iran and on the threat of Islamic extremism. Doug Bloomfield, who served as legislative director for Aipac in the 1980s — and who was pushed out, he says, for being “too pro-peace” — describes Aipac and other groups as “very sycophantic toward the Bush administration.” Aipac and other groups found little to criticize in a president who, unlike Bill Clinton, did not believe in pushing Jerusalem to make serious compromises to achieve peace. President Bush, in this view, was the best president either Israel’s Likud leadership or the mainstream Jewish groups could have wished for.

And it was precisely this success that began to loosen the “stranglehold” described by Mearsheimer and Walt. As Martin Indyk, a former American ambassador to Israel and now the director of foreign policy at the Brookings Institution, puts it, “In the Bush years, when Israel enjoyed a blank check, increasing numbers of people in the Jewish and pro-Israel community began to wonder, If this was the best president Israel ever had, how come Israel’s circumstances seemed to be deteriorating so rapidly?” Why was Israel more diplomatically isolated than ever? Why had Israel fought a savage and apparently unavailing war with Hezbollah in Lebanon? Why were the Islamists of Hamas gaining the upper hand over the more moderate Fatah in Palestine? “There was kind of a cognitive dissonance,” Indyk says, “about whether a blank check for Israel is necessarily the best way to secure the longevity of the Jewish state.”

Many liberal Jews have long chafed at the premise that Aipac or the Anti-Defamation League represented their point of view. Bush got only a quarter of the Jewish vote in 2004 and was deeply loathed by the most liberal-leaning voters. The community began searching for new ways to represent itself. Existing progressive groups like the Israel Policy Forum issued position papers or agitated for a change in policy; but scarce few did the yeoman labor of lobbying. Tom Dine, a former Aipac executive director, says he was approached in 2006 by a group of liberal Jewish philanthropists about heading a “counter-Aipac.” That idea went nowhere, but in late 2006 a different group of philanthropists and activists, including Ben-Ami, began to talk about combining the progressive organizations into a more powerful and influential collective body. Out of these conversations came J Street, named after the street missing from Washington’s grid and thus evoking a voice missing from Washington’s policy discussions. Early financing came from Alan Sagner, a retired New Jersey real estate developer and longtime supporter of Democratic candidates and Jewish causes, and from Davidi Gilo, an Israeli-American high-tech entrepreneur; another 50 early backers each gave $10,000. Unlike the liberal advocacy or policy organizations (or Aipac, for that matter), the new group would endorse and finance candidates, through a body called J Street PAC.

Ben-Ami is a political junkie who, at age 14, handed out leaflets for Jimmy Carter. He has worked in New York City government and politics; he served as deputy domestic-policy adviser in Bill Clinton’s first term and national policy director on Howard Dean’s presidential campaign. But he also benefits from an unusual Israeli pedigree. His great-grandparents joined the first group of Russian Jews to make aliyah — to move to the Holy Land — in 1882. His grandparents were among the 66 families that in 1909 drew seashells from a hat — the legendary Seashell Lottery — to parcel out sandy lots in what was to become Israel. His father served as a commander for Betar, the youth arm affiliated with Irgun, the fervent nationalist movement that fought the British to gain Israel’s independence. Ben-Ami’s father was tasked with purchasing the Altalena, a naval vessel left over from World War II that was then filled with arms and was on its way to Palestine when David Ben-Gurion declared the independent state of Israel and ordered all fighters to accept the authority of the state. After Menachem Begin, the head of Irgun, refused to turn back the Altalena, it was sunk by Ben-Gurion’s forces, led by Yitzhak Rabin. Ben-Ami, who was born in New York, says, “I grew up with my father spending his entire life arguing with his friends about the Altalena and Ben-Gurion and what a schmuck he was and how could Begin give back the Sinai.”

This is the world that shaped the mainstream American Jewish groups. Abraham Foxman, the head of the Anti-Defamation League, was born in Poland in 1940, and he often sounds as if only eternal vigilance will ward off the Holocaust in the offing. Morton Klein, president of the Zionist Organization of America, was born in a camp for displaced persons, to parents who were Holocaust survivors. The prophetic voice comes naturally to such men. So does the sense of besetting peril. Important Jewish organizations are normally reached through a series of locked doors presided over by glassed-in functionaries. The peril may be real. But it can also feel like a marketing device. “You know what these guys are afraid of?” says M. J. Rosenberg, Washington director of the Israel Policy Forum. “Their generation is disappearing. All the old Jewish people in senior-citizen homes speaking Yiddish are dying — and they’re being replaced by 60-year-old Woodstock types.”

J Street, by contrast, is wide open to the public. Visitors must thread their way through a graphic-design studio with which the organization shares office space. There appears to be nothing worth guarding. The average age of the dozen or so staff members is about 30. Ben-Ami speaks for, and to, this post-Holocaust generation. “They’re all intermarried,” he says. “They’re all doing Buddhist seders.” They are, he adds, baffled by the notion of “Israel as the place you can always count on when they come to get you.” Living in a world of blogs, they’re similarly skeptical of the premise that “we’re still on too-shaky ground” to permit public disagreement. There’s a curious and striking analogy with the situation of Cuban-Americans, whose politics until quite recently were dominated by the generation that fled Castro’s revolution and were grimly determined to see his regime overthrown. Obama has not had to pay a price for moderating the American embargo, as his predecessors would have, because Cuban-American opinion is no longer in thrall to the older generation — precisely J Street’s goal in regard to the Middle East.

Street PAC sent out a questionnaire to Congressional candidates in the summer of 2008, seeking their views on U.S. engagement with the Middle East. The group ultimately decided to support 41 candidates (most of them non-Jewish) and raised $580,000 in barely six months. A lot of the money came in small donations over the Internet, another sign of the organization’s new-generation status. And the money has continued to flow. This past June, several Jewish leaders were quoted in Politico as being disappointed in Donna Edwards, an African-American freshman legislator from suburban Maryland whom J Street had endorsed last year. Edwards voted merely “present” on a resolution supporting Israel’s assault on Gaza, and she criticized Israel’s settlement policy during a visit to the region. Edwards’s supporters feared she could face a primary challenge from a more pro-Israel candidate. As soon as the Politico item appeared, Ben-Ami fired off a fund-raising appeal to the J Street netroots. “This is exactly how — for decades — established pro-Israel groups have enforced right-wing message discipline on Israel in Congress,” he wrote. “But not this time — and not to our friend Donna Edwards.” Edwards, who says that her own views place her “right where the administration is” on Israel-Palestine issues, attracted $30,000 via J Street PAC’s appeal in three or four days. That made people in Washington take notice. It also infuriated some established leaders. One of them told me that any group that would raise money for the likes of Edwards “is not a responsible Jewish organization.”

On the fundamental questions of Middle East peace, J Street occupies fairly traditional liberal territory, which of course places it well to the left of the mainstream groups. According to its “statement of principles,” the group favors “creation of a viable Palestinian state as part of a negotiated two-state solution, based on the 1967 borders with agreed reciprocal land swaps” — the formula envisioned by the Clinton administration in its 2000 negotiations with Yasir Arafat and Ehud Barak. Ben-Ami says he also favors Jerusalem as the shared capital of the two states. On the question of talks with Hamas, classed as a terrorist organization by the United States and the European Union, J Street takes the cautious view that while we should not speak directly with officials, we should engage through intermediaries with the goal of finding interlocutors willing to live in peace with Israel.

J Street maintains that most American Jews share its views on the Middle East. They are reliably liberal on questions of war and peace; three-quarters of Jewish respondents to a 2007 Gallup poll, for example, opposed the war in Iraq. The question is how much of an exception they make for Israel. J Street sought to answer this question by commissioning an extensive poll of Jewish opinion on Middle East issues. The survey, taken in July 2008 and repeated with almost identical findings in March, found that American Jews opposed further Israeli settlements (60 percent to 40 percent), that they overwhelmingly supported the proposition that the U.S. should be actively engaged in the peace process even if that entailed “publicly stating its disagreements with both the Israelis and the Arabs” and that they strongly supported doing so even when the premise was revised to “publicly stating its disagreements with Israel.” Strikingly, the average respondent placed Israel eighth among a list of concerns; only 8 percent placed it first or second.

J Street specializes in mounting campaigns that may appeal to the 92 percent who care about other causes more than they do about Israel. Last September, the organization asked supporters to sign a petition demanding that sponsors revoke an invitation to Sarah Palin to speak at an otherwise nonpartisan rally on Iran. J Street says that more than 25,000 people signed it in 24 hours. (The invitation was revoked, though Malcolm Hoenlein, who helped organize the event, says J Street had nothing to do with it.) J Street generated a similar response when it sent out a bulletin warning of legislation that could result in a blockade of Iran, which critics argued could have led to war. Ben-Ami also posted links to John Hagee’s more outrageous statements as a reminder of the kind of company the mainstream organizations were keeping.

The most controversial and significant of J Street’s campaigns was the one most directly tied to Israel’s security. When Israeli fighter planes first hit Gaza on Dec. 27, J Street issued a press release stating that “there is no military solution to what is fundamentally a political conflict” and calling for “immediate, strong diplomatic intervention” to negotiate a resumption of the cease-fire. The next day, in a message to supporters, J Street’s campaigns director, Isaac Luria, wrote that “while there is nothing ‘right’ in raining rockets on Israeli families or dispatching suicide bombers, there is nothing ‘right’ in punishing a million and a half already-suffering Gazans for the actions of the extremists among them.”

J Street’s stand cemented its position on the left side of the spectrum; Ben-Ami says that the group’s list of supporters grew to 100,000, from 90,000. The group was, inevitably, denounced on the right. But it was denounced from the middle as well. Rabbi Eric Yoffie, the president of the Union for Reform Judaism and a natural ally, writing in a more-in-sorrow-than-in-anger op-ed in The Forward, described Luria’s sentiments as “morally deficient, profoundly out of touch with Jewish sentiment and also appallingly naïve.” In retrospect, Yoffie now says: “J Street missed the overwhelming support from the American Jewish community for the war in Gaza. This was their first big test, and they flunked the test.”

Ben-Ami does not agree, but he acknowledges that moments of crisis for Israel tap into the ancestral impulses. “There’s a rational side that on policy grounds is with us and Obama,” he says, “and can understand that talking, peace, these are good things, and they’re better than pre-emptive military action. Then there’s their grandmother’s voice in their ear; it’s the emotional side and the communal history, and it’s the fear of not wanting in some way to be responsible for the next great tragedy that will befall the Jewish people.”

This in turn raises a question about J Street’s prospects. As a lobbying group, would you rather represent the passionate few or the dispassionate many? The National Rifle Association knows the answer to that question. One administration official involved with the Middle East points out that Aipac cultivates single-issue partisans. Wielding the other 92 percent into a potent political force, he notes, will be “a major, long-term and uphill task.” He adds, “I’m not sure it can be done.”

Street’s most difficult challenge may be to raise the profile of what Ben-Ami calls the “pro-Israel, pro-peace” position on Capitol Hill. In late January, J Street helped circulate a resolution by Representative Bill Delahunt of Massachusetts, praising the administration for the appointment of George Mitchell — a means, Ben-Ami says, to allow legislators who felt compelled to sign on to the Gaza resolution to “do something positive.” In late May, an Aipac letter asking President Obama to ensure that America remains a “devoted friend to Israel” and to condition peace talks on an end to violence by Palestinians attracted 329 legislators. J Street responded several days later with a letter calling for active American engagement in the peace process and in helping to create effective governance in the Palestinian territories. That letter got 87 signatories. The lopsided tallies were telling. There’s a clear downside to being seen as the answer to the Israel lobby; Ben-Ami says, “I’m very consciously not interested in portraying our organization as anti-Aipac.” Of course, J Street’s counter-letter probably muddied those waters.

Robust debate has not, in fact, broken out on Capitol Hill. When I asked a senior Congressional staff member whether she felt that legislators were now prepared to say what they think on the Middle East, she replied, “I don’t think we’re there yet.” But, she added, “There are changes in the playground.” The tone of the debate over Gaza, for example, was slightly less one-sided than usual. Howard Berman, the chairman of the House Foreign Affairs Committee and a leading supporter of Israel, stated that while he had “no trouble justifying the war that Israel has undertaken,” he was “deeply troubled by the suffering, destruction and loss of innocent life that it inevitably entails.” The resulting resolution — with Israel, there are always resolutions — was an odd hybrid of typically bellicose “whereas” clauses (“whereas Hamas was founded with the stated goal of destroying the state of Israel”) and moderate “resolved” clauses calling for, among other things, the establishment of “a viable, independent and democratic Palestinian state.” A Congressional aide told me that Berman’s predecessor, Tom Lantos, permitted Aipac’s lobbyists to write the crucial language of resolutions and legislation, but Berman’s staff solicited comments from a wide range of groups, including J Street, and wrote the document themselves.

Even J Street’s staunch friends on the Hill acknowledge the potential costs of their position. Steve Cohen, a Democratic congressman who represents Memphis, told me that in his mind Israel had squandered its heroic status through its wars in Lebanon and Gaza and had come to be seen as “the neighborhood bully.” But he recalled that “when J Street first surfaced, the talk among members was, ‘Do we get near them?’ ” The organization had endorsed Cohen and asked if he would record a video for its Web site. “Several veteran Jewish members cautioned me not to do it,” he said. “They were afraid I would be attacked by Aipac. Some people whispered about the possibility of having an opponent.” He went ahead and made the video. He also signed the J Street letter calling for deeper American engagement in the peace process. I asked if there had been any repercussions. “I’m thinking about it,” said Cohen, a significantly wryer-than-average legislator. “I did have some strong Aipac supporters who didn’t come to my last fund-raising party. And they’re normally the first people to come forward.”

The acid test came in May when Netanyahu came to see Obama. The prime minister asked Obama to set a time limit on negotiations with Iran, whose nuclear aspirations Israel deeply fears, while Obama pressed his counterpart to place a total freeze on settlement expansion. Obama said he would review his Iran policy should Iran remain recalcitrant; Netanyahu did not make any pledges on settlements. Afterward, Netanyahu held a series of meetings on Capitol Hill. At a session with Jewish legislators, according to a senior lawmaker, Netanyahu was told: “You cannot ignore what the White House is raising about settlements. You have got to work it out with them.” This was scarcely a sharp rebuke, but neither was it the message that the prime minister had grown accustomed to hearing from Republican leaders in the 1990s, the last time he had held office.

President Obama has continued to use unequivocal language on settlement expansion, most notably in the speech he delivered in Cairo in early June. And mainstream organizations have continued to rally to Israel’s defense. In early August, the Anti-Defamation League took out a full-page ad in The New York Times and other dailies with the banner headline, in all capitals, “The Problem Isn’t Settlements; It’s Arab Rejection.” This has posed an agonizing problem for Jewish legislators who do not want to have to choose between Israel and the president. Shortly before the Cairo speech, Gary Ackerman, a New York Democrat who leads the Middle East and South Asia subcommittee of the House Foreign Affairs Committee, put out a press release headlined “Ackerman Urges Freeze on Settlement Construction, Not Growing Families.” This formulation is typically a coded way of advocating “natural growth” in the settlements. Soon after, however, Ackerman explained that he meant that families should keep growing — not exactly a contested principle — but that settlements should not. Ackerman told me that he views settlement expansion as “the irritant of the day,” and that whatever the merits, “the Arab world needs to see a sign that we understand their concerns.” You can almost hear the sound of elastic stretching as legislators are pulled in opposite directions.

This is not, at least on the surface, a very opportune moment for peace-making in the Middle East. Netanyahu’s immediate predecessors, Ehud Olmert and Ariel Sharon, both painfully came to the conclusion that Israel could not survive as a democratic and Jewish nation unless it was willing to allow a viable Palestinian state to be established — which in turn would require abandoning settlements. Netanyahu gives few signs of having internalized this inexorable logic. After returning from his visit to Washington, Netanyahu delivered a speech in which, for the first time, he endorsed a two-state solution, but his language remained as unyielding as ever. The speech, one senator said disgustedly, was “a totally wasted opportunity.” Netanyahu has refused to agree to an absolute freeze on settlements, despite sending some accommodating signals.

But the problem is scarcely limited to Israel. The Arab leaders on whom Obama is counting to help bankroll an emerging Palestinian state, to put pressure on Hamas and to respond to whatever gestures are made by Israel have been unwilling to step forward. Though the Palestinian leader, Mahmoud Abbas, appears to have been strengthened by his Fatah movement’s recent general congress, he is still far too weak to take on Hamas, which controls Gaza and fought Israel to a political standstill at the beginning of this year. The very real danger posed by Hamas, though the group seems quiescent at the moment, makes Israel profoundly reluctant to make significant concessions.

Even so, Middle Eastern dynamics are shifting. Like Israel, mainstream Arab states are worried about Iran and want American support for a hard line toward Tehran and its nuclear ambitions. The Palestinian problem is an obstacle to uniting against Iran. Indeed, Netanyahu himself has tried very hard to change the subject from Palestine to Iran. But that won’t fly either in Riyadh or in Washington; as the Cairo speech demonstrated, White House officials recognize that they must make real progress on Israeli-Palestinian peace in order to regain credibility in the Middle East. Such progress, they believe, will be possible only if Netanyahu curbs the settlements, which Palestinians and the larger Arab world see as part of an ongoing effort to alter “facts on the ground” to preclude a two-state solution.

Netanyahu has played a key role in that effort; and yet many Middle East experts see him as a canny calculator who recognizes full well that he cannot afford to be seen as having “lost Washington.” If Obama can extract a genuine, binding commitment on settlement growth from Netanyahu, he can then turn to Palestinian and Arab leaders for concessions sought by Israel. Reciprocal gestures would in turn create momentum toward solving the yet-more-difficult final-status questions of mutual borders, the status of Jerusalem and the “right of return” for Palestinians who fled Israel decades ago. Israeli-Palestinian negotiations continue to flag, but there has been hopeful talk that the Obama administration may seek to bring Netanyahu and Abbas together when they are in New York later this month for the United Nations General Assembly meeting.

J Street, in short, will not lack for acreage to till. The organization promised its supporters that between August and Labor Day it would take “50,000 actions” to support the president’s policies. By late August, it was able to report that “we’ve sent 29,243 e-mails, made 1,288 calls and told 2,596 friends about our work.” Meanwhile, Ben-Ami was beginning to build up a network of local supporters who could give legislators a piece of their mind — just as Aipac has (only much smaller). He is bringing highly placed Israeli peaceniks to spread their alternative message in Washington and beyond. And J Street’s new corps of lobbyists will soon be fanning out into the wilds of Congress, there to sit down with legislators and staff who have never heard of, much less met with, liberal advocates on Israel.

J Street may still be too small a blocking back to clear much of a path for the Obama administration. But you can compensate for size if you’re not afraid of contact.