The first national conference of J Street, the self-described “pro-Israel, pro-peace” lobby, convened October 25 in Washington, D.C., with all the understated reserve of a new iPhone launch or the christening of the Queen Mary. Gathered in a swank hotel a short walk from the White House, some 1,500 activists from across the country sat through hours of speeches by big-shot politicians and diplomats, earnestly debated tactics and philosophy, handed out awards over chicken dinners and jabbered excitedly in the corridors. Outwardly it looked like any other major Jewish organization rallying its troops and flexing its muscles.

But this was, as J Streeters boasted and critics complained, no ordinary Jewish convention. These conventioneers were rallying not to defend Israeli actions and reaffirm Jewish virtue but to challenge and question. It’s no easy trick these days to convince 1,500 Jewish liberals to pay their own way to Washington for the purpose of fighting over Jewish values. J Street’s success in pulling it off surely earns them some bragging rights, whatever one thinks of their positions.

Up to a point, that is. J Street’s conference was an impressive feat, but it’s not quite the game-changer it’s been made out to be — at least, not yet. On examination, this shiny new vehicle turns out to have a few kinks built into its design. They’ll have to be addressed if the organization hopes to succeed.

The core problem is that J Street has two main stated goals, and they don’t really fit together. The first goal is to “broaden” the definition of what it means to be pro-Israel, to open up Jewish community discourse to a wider range of acceptable opinions. The second goal is to lobby for an Israeli-Palestinian peace accord that leads to a two-state solution. It became evident during the convention that you can’t do both.

By advertising itself as a forum for free and open discussion of Israel, warts and all, the conference predictably attracted a contingent of Jews who are ambivalent or hostile toward Israel. They weren’t on the program, but they spoke up in breakout sessions and gathered in clusters in the hallways. Some came to paint Israel as the guilty party and argue for sweeping Israeli concessions without regard for Israel’s security. Some opposed the very idea of Jewish statehood. Most came to Washington expecting to help shape J Street’s goals and gain political influence for their views.

What they found was an organization that defines itself as wholly committed to Israeli security, that favors an Israeli-Palestinian accord as a way to ensure Israel’s security as a Jewish state. If that wasn’t obvious beforehand, J Street’s architect and executive director, Jeremy Ben-Ami, pointedly drew a line in the sand in an October 23 interview with journalist Jeffrey Goldberg (full disclosure: not me) on the Web site of The Atlantic.

Sounding more hawkish than he had in the past, Ben-Ami ruled out cuts in American military aid to Israel, endorsed the Law of Return, denounced the so-called “one-state solution” and repeatedly distanced himself from individuals and groups on the left that reject Zionism. Arriving at the conference two days later, the outliers — let’s call them “un-Zionists” — were in an ornery mood, feeling duped and gobsmacked. In one breakout session on how broadly to define “pro-Israel” (full disclosure: this was moderated by yours truly) one audience member emotionally protested the very idea that she should define herself as pro-Israel. At another session, a participant objected to the suggestion that advocates of territorial compromise should emphasize their love of Israel. Some greeted Rabbi Eric Yoffie of the Union for Reform Judaism with boos when he criticized the Goldstone report.

All this left J Street in a ticklish position. By calling for unfettered debate, it had essentially invited the un-Zionists to come and participate. Objecting to their presence would undercut its declared commitment to open discussion. But embracing them would undermine its credibility as a pro-Israel organization advocating compromise as a means to strengthen Israel’s security, not weaken it. Ben-Ami and others argued that a firm pro-Israel stance would make the un-Zionists want to leave. But the un-Zionists gave no sign that they would leave willingly. J Street could be in for a fight that will leave it tainted with a McCarthyite image in the eyes of some liberals it needs to recruit.

The hard truth is that both of J Street’s goals are important. Growing numbers of American Jews are struggling with their relationship to Israel. They shouldn’t be cast out. The community urgently needs a forum for members to engage over their differences rather than turn their backs on one another. It also needs a strong voice for security through peace and compromise. But they’re two different jobs. One vehicle can’t do both.