Bill Kristol (Salon/Fox News)

The Emergency Committee for Israel, an advocacy group launched by Bill Kristol and other neoconservative activists, and J Street, the 2-year-old outfit that bills itself as a liberal "pro-Israel, pro-peace" voice, recently aired dueling ads about Joe Sestak, the Democratic nominee for Senate in Pennsylvania.

The Emergency Committee went first, with a menacing spot that asked, "Does congressman Joe Sestak understand Israel is America’s ally?" J Street's defensive response was telling. "In Congress, Sestak consistently votes to aid Israel," the group informed Pennsylvanians.

The ad, needless to say, didn't bother to question why the U.S. should be spending so much money on Israel in the first place. So much for challenging the assumptions of the pro-Israel establishment.

J Street, which launched in April 2008 to great fanfare under the helm of Jeremy Ben-Ami, a former advisor to President Bill Clinton, was founded in part to "ensure a broad debate on Israel and the Middle East in national politics and the American Jewish community." That debate has largely been dominated by unquestioning supporters of Israel and all its actions.

But despite the hysterical rhetoric from the likes of Alan Dershowitz and Commentary magazine, who like to claim that J Street is agitating for radical policy change, the new group has done little to broaden the constricted U.S. debate over Israel/Palestine.

Instead, J Street has largely given a liberal cover to more right-wing groups like the American-Israel Public Affairs Committee, whose line seems to be one of supporting Israel no matter what.

The Goldstone report, a landmark U.N. document that accused both Israel and Hamas of committing war crimes during the 2008-09 Israeli assault on Gaza, and the boycott, divestment and sanctions (BDS) movement that seeks to pressure Israel to live up to its obligations under international law, are two areas where the J Street line has differed little from AIPAC.

The debate over the Goldstone report was an early indicator of things to come for J Street. When a largely fact-free congressional resolution denouncing the report was about to pass, J Street, which aired some concerns about the resolution and urged Congress to modify it, still ultimately agreed with the thrust of it: "J Street supports passage of a resolution by the U.S. Congress calling for the United States to oppose and work actively to defeat one-sided and biased action in the United Nations when it comes to Israel and the Goldstone Report." That statement was similar to AIPAC’s position on the report, who called it "deeply flawed" and "rigged."

J Street's acquiescence to the establishment line on Israel/Palestine reached its zenith during the University of California at Berkeley debate in March/April 2010 over a student effort to divest from two companies that profit from the Israeli occupation of Palestine. When the president of the student government at Berkeley vetoed the measure, which was passed earlier by an overwhelming margin, J Street joined AIPAC, the Anti-Defamation League and the local Israeli consul general in pressuring the student government. J Street joined a wide coalition of groups such as the David Project and the Jewish National Fund that authored a letter labeling the divestment measure as "misleading" and "dishonest." (J Street’s president, Jeremy Ben-Ami, has since said that the group won’t be signing on to similar letters with "organizations like that in group settings again.") Their effort worked -- a measure to override the veto failed by just one vote.

This timidity has earned J Street harsh criticism from the left. An Israeli-authored letter circulated on an activist listserv called on the group to "stop trying to gain political capital at the expense of dedicated peace activists."

It is also creating a vacuum that older, more left-leaning groups like Jewish Voice for Peace are poised to fill. This third pole, which has emerged underneath the surface, is challenging the pro-Israel lobby’s hold on the debate. The future battle, especially in the Jewish-American community, will not be J Street vs. AIPAC, but rather the pro-Israel lobby vs. critical Jewish groups who are questioning the desirability of the U.S.-Israel "special relationship."

The divestment debate at Berkeley and the criticism of J Street is a prominent example of the new battle that is coming to a head within the Jewish community over Israel/Palestine and the Palestinian-led call to boycott, divest from and sanction Israel. The BDS movement started in 2005, and calls on global civil society to use the tactics of boycotting, divesting and sanctioning Israel until it adheres to its obligations under international law. The movement demands that Israel withdraw from the occupied Palestinian territories, implement equal rights for Palestinian citizens of Israel and recognize the "right of return" for Palestinian refugees and their descendants who fled or were expelled from Palestine during the 1947-49 Israeli-Arab War.

The debate over BDS is heating up. Recently, Jacob Weisberg, the editor in chief at Slate, called the BDS movement "a weapon designed not to bring peace but to undermine [Israel]" and "hard to disassociate from anti-Semitism." The smearing of the BDS movement as anti-Semitic, though, is increasingly losing credibility, especially because groups such as Jewish Voice for Peace and others are backing aspects of the movement. In its latest issue, Tikkun magazine published a debate on BDS between Ben-Ami, Jewish Voice for Peace’s Rebecca Vilkomerson and others, an indication of the growing importance of the movement.

During the Tikkun debate, Ben-Ami argued that those opposed to the Israeli occupation should not engage in BDS tactics that alienate Israelis and should instead "double down on our movement to try to get particularly President Obama to be deeply and actively engaged to outline what a solution is." But with peace talks at a standstill, and President Obama averse to pressuring Israel, the BDS movement will only gain steam -- with or without J Street on board.

The momentum was evident just a few months ago, after the Israeli Navy raided an aid flotilla on its way to Gaza and killed nine people, when a wave of music acts honored the cultural boycott, and garnered attention from major media outlets like the Associated Press and CNN.

While it’s hard to predict when mainstream discourse will allow candid discussion about Israel/Palestine, cracks in the wall are appearing, and they’re only going to get bigger.