As John Kerry’s bid to broker Israeli-Palestinian peace approaches its moment of truth, you can sense the desperation among liberal Zionists. “Kerry’s mission is the last train to a negotiated two-state solution,” declared Thomas Friedman in January.

“This is a watershed moment after which Israel will face a completely different situation - one which will be governed by new realities much less favorable than those Israel faces today,” argued the philanthropist S. Daniel Abraham that same month. Kerry himself has said that, “If we do not succeed now, we may not get another chance.”

I get it. You have to be blind not to see that liberal Zionists—those of us who believe in the legitimacy of a state dedicated to Jewish self-protection and the illegitimacy of Israel’s unjust, undemocratic control of the West Bank—are losing ground to one-staters at both ends. Kerry’s failure, which might spell the end of the American-led peace process itself, could turn that retreat into a rout.

But there’s a problem with being desperate for a deal: You lose your leverage over its content. Kerry and the rest of the Obama foreign policy team know that if they present a framework that Benjamin Netanyahu dislikes, he and the right-leaning American Jewish establishment will make their lives miserable. If, on the other hand, they present a framework that tilts against the Palestinians, the resulting Palestinian outrage will be far easier to withstand. That’s partly because Palestinians wield little influence in Washington. And it’s partly because we liberal Zionists—desperate to see Kerry succeed—have given every indication that we’ll support whatever he serves up, the particulars be damned.

The consequences of this political imbalance have been quietly playing themselves out for months now. Numerous press reports have suggested that Kerry is contemplating a framework that offers the Palestinians substantially less than what Bill Clinton offered them in December 2000 and what Ehud Olmert offered in 2008.

The Clinton parameters, for instance, called for Israeli troops to leave the Jordan Valley—the twenty-five percent of the West Bank that abuts its border with Jordan— within three years of a peace deal. Olmert was willing to withdraw them even faster

Mahmoud Abbas is also reportedly calling for a transition of three to five years. Netanyahu, by contrast, depending on whose reporting you believe, insists that Israeli troops must remain for ten or even forty years. 

And Kerry? Palestinian sources say he’s endorsed the ten-year timetable. According to the Washington Post, he’s suggested somewhere between five and fifteen

Kerry’s proposal, in other words, violates both the Clinton parameters and the understanding reached by Olmert and Abbas. Yet with rare exceptions, liberal Zionists aren’t protesting at all.

That’s just the beginning. When it comes to Jerusalem, the Clinton Parameters declared that, “the general principle is that Arab areas are Palestinian and Jewish ones are Israeli.” 

According to Bernard Avishai, Olmert and Abbas agreed to the same concept: “Jewish neighborhoods [of Jerusalem] should remain under Israeli sovereignty, while Arab neighborhoods would revert to Palestinian sovereignty.” 

And Kerry? In January, Israeli television reported that he had offered to locate the Palestinian capital in only one, relatively remote, neighborhood of East Jerusalem. (Either Isawiya, Beit Hanina, Shuafat or Abu Dis, which is not even in Jerusalem at all). Late last month, the Palestinians leaked that Kerry had again offered them a capital in Beit Hanina alone

Notice a pattern? Once again, assuming the reports are true, Kerry is pulling back from the principles established by both Clinton and Olmert. And once again, liberal Zionists are cheering him on.

It’s the same with refugees. To be sure, neither Clinton nor Olmert believed vast numbers of Palestinians who had fled their homes during Israel’s war of independence would return. The Clinton parameters declared that while a newly created Palestinian state “would be the focal point for Palestinians who choose to return to the area,” Israel would “establish a policy so that some of the refugees would be absorbed into Israel consistent with Israel’s sovereign decision.” Olmert translated that into numbers. He said Israel could accept 15,000 refugees. (Abbas wanted perhaps ten times as many). 

But neither Clinton nor Olmert took the position that no Palestinians could return at all. Yet according to several reports, Kerry has done just that.

Similarly, the Clinton Parameters say nothing about the Palestinians recognizing Israel as a “Jewish state.” (As opposed to merely recognizing Israel, which the PLO did in 1993). And while Olmert did raise the “Jewish state” issue, he didn’t accord it the centrality Netanyahu has. It’s not even clear that he included the demand in the final peace proposal he offered Abbas. Yet, Kerry, according to multiple leaks, has made Netanyahu’s “Jewish State” demand his own.

You have to hand it to Netanyahu. He has steadfastly rejected the axioms that guided Israeli-Palestinian negotiations in the past. (Remember, he still hasn’t even accepted the principle of the 1967 lines plus land swaps). In so doing, he has so shifted the terms of debate that positions once considered too radical for an Israeli prime minister to espouse are now considered American compromises.

But the result may deeply self-defeating. Even before these latest talks, Mahmoud Abbas had already recognized Israel’s right to exist, eschewed violence, acknowledged that Israel would control the Jewish neighborhoods of East Jerusalem, accepted that some Israeli settlements could stay in return for land swaps, said a Palestinian state would have no real army and declared that Palestinian refugee return could not transform Israel’s “social composition.” 

These concessions have damaged Abbas politically; many Palestinians already consider him a sell-out. Pushing him further is not just bad for the Palestinians. It’s bad for Israel. No credible Palestinian leader can leave most of Palestinian East Jerusalem under Israeli control or bless long-term Israeli control over the eastern border of a Palestinian state. Even if Kerry and Netanyahu could somehow bludgeon Abbas into accepting those terms, the result would be a crippled leader of a non-viable state.

More likely, if the reports about what Kerry is contemplating are true, Abbas will refuse - and via international lawsuits and economic boycotts, move the Israeli-Palestinian conflict into arenas where Israel is more vulnerable. The American Jewish right will triumphantly declare that, yet again, the Palestinians have rejected peace. And liberal Zionists, having written John Kerry a blank check, will be utterly at sea.

Right now, before the Kerry mission comes any closer to fruition, J Street should declare its support for the Clinton parameters and the (partial) understandings reached by Olmert and Abbas. The next time a newspaper reports that Kerry is caving to Netanyahu and insisting that Abbas make concessions that go beyond what he was asked to accept in past negotiations, J Street should raise a stink. In so doing, it would show the White House, and its own members, that being a liberal Zionist does not mean slavishly supporting whatever diplomatic proposal an American administration gins up. It means supporting a genuinely viable Palestinian state, one that is economically and politically strong enough to offer Palestinians a decent future, a decent future that will help safeguard Israel’s as well.

Failing to reach a deal would not be the worst outcome of Kerry’s diplomatic crusade. The worst outcome would be for America to endorse a deal that is unworkable and unjust. It’s time for liberal Zionists to starting saying that now, while there’s still time.