Most people agree that a settlement freeze in the West Bank is a minimum precursor to any sort of a peace deal.  Except the Israeli government, that is, which has gone right along expanding the settlements since the beginning of Oslo.  In the early 1990s, there were something like 100,000 people in West Bank settlements; now that number is nearing 300,000, plus several hundred thousand more in annexed East Jerusalem, and growing:

The failure of slow-motion diplomacy can be told in numbers. In 1993, when the Oslo process began, 116,000 Israelis lived in the Gaza Strip and the West Bank (excluding Israeli-annexed East Jerusalem). Seven years later, when negotiations collapsed, the settler population had risen to 198,000.

Watching this steady march, Ehud Olmert, then Ariel Sharon's deputy prime minister, stunned Israelis in late 2003 by renouncing his lifelong commitment to keeping Gaza and the West Bank under Israeli rule. "We are approaching a point where more and more Palestinians will say: 'There is no place for two states between the Jordan and the sea,'" he warned. Instead, he said, they would demand equal rights in a single, shared political entity--one person, one vote. The only way to preserve a Jewish state was to withdraw, he argued. By then, according to the Israeli Interior Ministry, there were 236,000 settlers.

Olmert's declaration presaged Sharon's decision to withdraw from Gaza. In 2006, Olmert was elected prime minister. Despite the Gaza evacuation, the settler population was then more than 253,000.

Last year, when Olmert resigned and elections were announced, the number of settlers in the West Bank had passed 290,000, living alongside 2.2 million Palestinians. (Another 187,000 Israelis lived in annexed East Jerusalem, next to 247,000 Palestinians.) By the time the next prime minister takes office, more than 300,000 Israelis are likely to be living in the West Bank, with the number continuing to climb.

There's a large and fascinating public choice literature on how politicians attempt to lock future politicians into their choices.  A good example might be the FDR's famous remarks about Social Security.  According to Luther Gulick,

Henry Morganthau showed no interest in the proosals and repeated all of the regular arguments on the sales tax ignoring the fiscal policy considerations arising at a time of high incomes and commodity shortage. I, therefore, discussed the problem with FDR when he asked me how I was coming with the Treasury study. He said to go ahead and explore the idea with Harold Smith, Marriner Eccles, and others.

In the course of this discussion I raised the question of the ultimate abandonment the pay roll taxes in connection with old age security and unemployment relief in the event of another period of depression. I suggested that it had been a mistake to levy these taxes in the 1930's when the social security program was orgiginally adopted. FDR said, "I guess you're right on the economics. They are politics all the way through. We put those pay roll contributions there so as to give the contributors a legal, moral, and political right to collect their pensions and their unemployment benefits. With those taxes in there, no damn politician can ever scrap my social security program. Those taxes aren't a matter of economics, they're straight politics."

So far, FDR has proven absolutely right.

Those who favored expanding the settlements have proven similarly able to lock Israel in.  The more settlers there are, the harder it is for the government to reverse its settlement policy, and the more the settlements grow, which makes the whole thing even more impossible.  It's hard to see, now, how Israel's fractious government can reverse itself.  Whatever the policy wisdom, it's political suicide.  There's another public choice lesson here:  while all Israelis have a stake in the settlement question, the people most affected are the settlers, and hence policy is very likely to follow their wishes.

I'd argue that this is not good for the State of Israel, for reasons others have exhausted.  Israel hasn't the political will for genocide all-out war forcible transfer, nor the support of the US, without whose military technology their formidable edge would erode.  But they can't simply occupy the West Bank forever.  After a certain point, they will be forced to recognize that they are the government of the West Bank.  And either give the Palestinians the vote, or decide not to be a Western democracy.  Either would destroy the conception that most hold of the State of Israel.

I think the time for a two state solution has probably already passed--I don't know anyone who gives a convincing rendition of a viable Palestinian state on the remaining territory.  The issue of water rights alone seems to be impossible.  All of the scenarios where everything works out sort of okay seem, to this outsider, to rest on some pretty big dose of fantasy:  one in which the settlements are pulled back, or Jordan agrees to take the bits Israelis don't want, or where the Palestinians, I don't know, kind of, just aren't there any more.