We have reached the first test of Israel's disengagement from Gaza -- and it comes from the Israelis, not the Palestinians. Today, Benjamin "Bibi" Netanyahu -- former Prime Minister and most recently Finance Minister -- announced that he is challenging Ariel Sharon for chairmanship of the Likud (and, by extension, to be the party's candidate for the premiership).

Bibi hopes to tap into the huge disenchantment with disengagement among the 3,000 members of the Likud Central Committee -- who, like primary voters in the US, are more extreme than the rank-and-file -- and defeat Sharon as party leader, inevitably forcing early elections. (For an excellent run-down of the events that could lead to the fall of Sharon, go here).

Recent polling shows that Bibi has more than a good shot at winning the Central Committee vote (he led a poll taken last week, 47 percent to 30.5 percent), but it may be a Pyhrric victory. Sharon is significantly more popular among the general electorate, and most likely could beat Bibi (and a weak Labor candidate) in a general election match-up. All he needs is a party to do so. This, in turn, has raised the possibility of Sharon forming a centrist party with the pro-disengagement Likudniks, hawkish Laborites, and the secular Shinui party (which is now the third-largest party in the Israeli parliament).

While recent experiments with centrist parties led by venerable Israeli leaders have not fared well (the Center Party won 5 percent of the vote in 1999 and quickly dissolved into the political landscape), none of them have been led by a sitting, popular prime minister. And none have appeared at a time as tense as this one.

A few weeks ago, Michael Lind floated that idea that the US was undergoing an electoral realignment. Josh, myself, and others chimed in that this was the furthest thing from the case, and in fact, there was a good amount of stasis in US political system. To see what the conditions for realignment are: one can look to Israel. The Gaza disengagement has crystallized cleavages within Israeli society -- between religious and secular, or as Hirsch Goodman of the Jaffee Center for Strategic Studies put it on NPR this morning, between consolidationists and expansionists. The current political system does not accurately reflect these divides; there's a precipitating critical event (Gaza disengagement); and the personalities needed to lead people out of there long-standing partisan attachments are there. Realignment seems possible.

As a political scientist, the prospect of such a transformation in Israeli politics is exciting (political scientists' search for realignments is only rivaled in intensity by astronomers' search for extra-terrestial life). But the significance goes way beyond the academic.

The outcome of this next election in Israel will have a huge impact on the shape of the Middle East. Relying so much on the right wing of Likud, a Netanyahu victory would embolden the expansionist and religious elements within Israel, and leave the rest of the electorate that yearns for security and hopes -- but not naively -- for peace without a clear leader or even a clear partisan choice. As with disengagement, Sharon is, improbably and once again, the indispensable man.