TEL AVIV — It is pretty clear now that Secretary of State John Kerry will either be Israel’s diplomatic salvation or the most dangerous diplomatic fanatic Israel has ever encountered. But there isn’t much room anymore for anything in between. This is one of those rare pay-per-view foreign policy moments. Pull up a chair. You don’t see this every day.

In essence what Kerry is daring to test is a question everyone has wanted to avoid: Is the situation between Israelis and Palestinians at five minutes to midnight or five minutes after midnight, or even 1 a.m. (beyond diplomacy)?

That is, has Israel become so much more powerful than its neighbors that a symmetrical negotiation is impossible, especially when the Palestinians do not seem willing or able to mount another intifada that might force Israel to withdraw? Has the neighborhood around Israel become so much more unstable that any Israeli withdrawal from anywhere is unthinkable? Has the number of Israeli Jews now living in East Jerusalem and the West Bank become so much larger — more than 540,000 — that they are immovable? And has the Palestinian rhetoric on the right of return become so deeply embedded in Palestinian politics? So when you add them all up, it becomes a fantasy to expect any Israeli or Palestinian leader to have the strength to make the huge concessions needed for a two-state solution?

President Obama is letting Kerry test all this. Kerry has done so in a fanatically relentless — I’ve lost count of his visits here — but highly sophisticated way. After letting the two sides fruitlessly butt heads for six months, he’s now planning to present a U.S. framework that will lay out what Washington considers the core concessions Israelis and Palestinians need to make for a fair, lasting deal.

The “Kerry Plan,” likely to be unveiled soon, is expected to call for an end to the conflict and all claims, following a phased Israeli withdrawal from the West Bank (based on the 1967 lines), with unprecedented security arrangements in the strategic Jordan Valley. The Israeli withdrawal will not include certain settlement blocs, but Israel will compensate the Palestinians for them with Israeli territory. It will call for the Palestinians to have a capital in Arab East Jerusalem and for Palestinians to recognize Israel as the nation state of the Jewish people. It will not include any right of return for Palestinian refugees into Israel proper.

Kerry expects and hopes that both Prime Minister Benjamin Netanyahu of Israel and Palestinian President Mahmoud Abbas will declare that despite their reservations about one or another element in the U.S. framework, they will use it as the basis of further negotiations.

This is where things will get interesting. U.S. and Israeli officials in close contact with Netanyahu describe him as torn, clearly understanding that some kind of two-state solution is necessary for Israel’s integrity as a Jewish democratic state, with the healthy ties to Europe and the West that are vital for Israel’s economy. But he remains deeply skeptical about Palestinian intentions — or as Netanyahu said here Tuesday: “I do not want a binational state. But we also don’t want another state that will start attacking us.” His political base, though, which he nurtured, does not want Netanyahu making a U-turn.

Which is why — although Netanyahu has started to prepare the ground here for the U.S. plan — if he proceeds on its basis, even with reservations, his coalition will likely collapse. He will lose a major part of his own Likud Party and all his other right-wing allies. In short, for Netanyahu to move forward, he will have to build a new political base around centrist parties. To do that, Netanyahu would have to become, to some degree, a new leader — overcoming his own innate ambivalence about any deal with the Palestinians to become Israel’s most vocal and enthusiastic salesman for a two-state deal, otherwise it would never pass.

“Nothing in politics is as risky as a U-turn or as challenging as a successful one,” says Gidi Grinstein, the president of the Reut Institute, a leading Israeli strategy group. “It requires a gradual disengagement from one’s greatest supporters, who slowly turn into staunchest enemies, while forming a new coalition of backers, made up of former opponents. In a cautious dance of two-steps-forward, one-step-back, U-turning leaders must shift their political center of gravity from the former base to their future platform.”If the Palestinians and Israelis find a way to proceed with the Kerry plan, everything is still possible. Success is hardly assured, but it will prove that it’s not midnight yet. But if either or both don’t agree, Kerry would have to take his mission to its logical, fanatical conclusion and declare the end of the negotiated two-state solution. (If not, he loses his credibility.)If and when that happens, Israel, which controls the land, would have to either implement a unilateral withdrawal, live with the morally corrosive and globally isolating implications of a permanent West Bank occupation or design a new framework of one-state-for-two-people.

So that’s where we are: Israelis and Palestinians need to understand that Kerry’s mission is the last train to a negotiated two-state solution. The next train is the one coming at them.