With two months left before the midterm elections, a hawkish group is targeting several congressional Democrats who last January signed a letter sponsored by J Street, the dovish Israel lobby, pressing the administration to get Israel to loosen its blockade of Gaza.

As the newly founded Emergency Committee for Israel airs attack ads against these congressional candidates, J Street is responding with a campaign of its own seeking to discredit the group as extreme and out of sync with the mainstream Jewish community.

In some ways, the spiraling ad war is seen as a test of J Street’s ability to give protective cover to those who work with it and, conversely, the ability of J Street critics to render the lobby radioactive. For both sides, it is also a battle over which congressional candidates are worthy of using the title “pro-Israel.”

ECI is currently going after five Democratic candidates. While most efforts are focused on the Pennsylvania Senate race, where ECI has repeatedly put out ads attacking candidate Joe Sestak, the group has also begun running ads against Jim Himes, who is in a close race in Connecticut; Glenn Nye in Virginia; Ohio’s Mary Jo Kilroy, and Rush Holt from New Jersey.

The five candidates were among the 54 members of Congress who signed the letter to the president last January, calling on the administration to get Israel to ease its Gaza siege, which blocked all but humanitarian goods from entering the Palestinian territory and allowed no exports out.

“Most members of Congress are friends of Israel. That’s why a huge majority, 88%, refused to sign a letter accusing Israel of collective punishment when Israel was defending its citizens from the terrorist group Hamas,” the TV ads put out by ECI claim. The ads then urge voters to call the candidate and ask why he or she joined “an assault on Israel.”

“There are candidates who claim they are pro-Israel but do things that are not pro-Israel, and we are drawing attention to their records,” said Noah Pollak, executive director of ECI. He said that the group is seeking races in which it can “make a difference,” and so chose to go after signers of the Gaza letter who are in close races and in districts where views on Israel could make a difference for voters in November.

The Gaza letter has emerged as the main criteria used by ECI to determine candidates’ views on Israel. The group, according to Pollak, is also looking at the candidates’ respective track records in Congress and at the organizations that support them.

The Gaza letter, initially sponsored by Democrats Jim McDermott from Washington and Keith Ellison from Minnesota, was supported by J Street and opposed by the American Israel Public Affairs Committee, and by the Israeli Embassy in Washington. In the letter, members of Congress spoke of the need to ease restrictions on goods entering Gaza as well as on the movement of individuals into the area and out of it. The blockade has been blamed for widespread impoverishment, hardship and medical distress in the territory. The Israeli government has since taken steps to revise its blockade policy on Gaza, some of which were in line with the demands the letter advocated.

But while the letter recognized Israel’s “legitimate and keenly felt fear” that led to imposing the restrictions, it also asserted that these concerns should be addressed without resulting “in the de facto collective punishment” of Palestinians in Gaza.

Some members who signed the letter had already come under fire, and one signatory, Rep. Yvette Clarke from New York, retracted her support because of pressure from her ultra-Orthodox Jewish constituency. Now, ECI wishes to further make the case that supporting views advocated by the dovish J Street lobby could come with a political price tag. “If you sign a letter like this, we will bring it to the attention of your constituents,” Pollak said.

ECI, which was launched earlier this summer, is committed, according to its mission statement, to “mounting an active defense of the U.S.-Israel relationship by educating the public about the positions of political candidates.” The group’s board features William Kristol, editor of conservative The Weekly Standard, and conservative Christian leader Gary Bauer. Michael Goldfarb, a Weekly Standard contributing editor who advised the 2008 John McCain presidential campaign, is also consulting for ECI.

While positioned in the media as the “anti-J Street,” ECI is careful not to relate directly to the dovish lobby. Still there are similarities: Both groups provide backing for candidates that adhere to their ideology, either by expressing support or by attacking their rivals. Yet while J Street, through one of its sister organizations, JStreetPAC, contributes directly to candidates, ECI does not endorse politicians.

J Street’s reaction to the emergence of ECI was initially limited to the Sestak race. The lobby issued counter ads praising the Pennsylvania Democrat for his views on Israel and provided increased fundraising for him through the public action committee, reportedly reaching $75,000.

The group maintains that while showing support for likeminded candidates is important, it would be wrong to believe that voters, even Jewish voters in close races, will determine their vote based on a candidate’s view on Israel.

“I don’t buy this premise, not even the premise that views on Israel are a contributing factor,” said Jeremy Ben-Ami, J Street’s executive director. Ben-Ami stressed that the group is not concerned about ECI’s decision to spend money on ads attacking candidates that were endorsed by J Street. “This is politics,” he said.

Four of the five politicians being targeted by ECI are on JStreetPAC’s endorsement list for this election cycle. So far, two of the candidates under fire have chosen to respond to the ads accusing them of not supporting Israel. Sestak gathered Pennsylvania Jewish leaders to vouch for his support for Israel and was backed by counter-ads run by J Street that highlighted his votes for foreign aid to Israel.

In Ohio, the Mary Jo Kilroy campaign responded angrily to the attack ads. On a website entitled “Is May Joe Anti-Israel?” which was funded by her campaign, the answer in bold letters is “No.” The website also urged supports to “let Bill Kristol and extreme right-wing friends know that spreading lies and misinformation won’t keep Israel safe.”

J Street, meanwhile, is taking aim at the people behind ECI, trying to portray them as being outside the Jewish community consensus. “I want it to be clear that this a political effort launched by radical neocons,” Ben-Ami said. To make the point, he asked to present ECI with a series of questions regarding its view on the Israeli government’s policy. “Does the Emergency Committee support a two-state solution? Do they support the opening of direct peace talks?” Ben-Ami asked.