Olmert is the most compellingly contradictory character in Israeli public life. But the seeming support for his comeback reflects a deeper contradiction of politics here: there is still a constituency for peacemaking, and certainly a constituency for replacing Netanyahu. It  just doesn't have a credible candidate.

Olmert, let's remember, inherited politics from his far-right Knesset-member father, and entered parliament at age 28 on the Likud ticket. For most of his career, you could have put his picture next to the word "cynicism" in the dictionary. He maintained a private law practice while in office, acquired rich friends, was charged with fraud in fundraising for the 1988 election but acquitted. During his tenure as Jerusalem's mayor, the city got dirtier and poorer, while Olmert racked up frequent-flier points.

Then, in 2003, as Ariel Sharon's deputy prime minister, Olmert had a Big Idea, new for him: Israel had to get out of Gaza and most of the West Bank, lest it become a binational state. As Sharon's successor and candidate of the new Kadima party, he led the center and left to winning a solid majority in the Knesset. As prime minister, he conducted talks on a two-state solution with Palestinian leader Mahmoud Abbas—talks that both he and Abbas say brought them close to agreement. Then the idealist's slimy past seemed to catch up with him: facing police investigations, he resigned. That paved the way for Netanyahu to take power. You had to look at Olmert twice—as an idealist, and as a fitting candidate for governor of Illinois—to see him once.

This summer, a Jerusalem court decided that reasonable doubt existed in two of the major corruption cases against Olmert and acquitted him. Pundits split into two camps: those who saw the judges as falling for a  fairy-tale defense, and those who saw the prosecution as responsible for driving a prime minister from office on flimsy evidence. Olmert supporters and critics of the prosecution suggested that right-wing American Jews provided at least part of this evidence in order to get rid of the peacenik prime minister.

So for Olmert to consider a comeback looks reasonable. Given that Olmert-the-idealist still wants to complete a two-state deal—an agreement that would end the moral folly of occupation, an agreement that Netanyahu has done all he can to avoid—it also looks reasonable for a moment or so that supporters of peace would welcome his comeback.

But only for a moment. Olmert is the prime minister who initiated the disastrous war in Lebanon in 2006. Besides that, he's still on trial on charges of taking bribes while mayor of Jerusalem. And besides that, the court that acquitted him last summer in two cases convicted him in a third: as a minister, he gave favored treatment to companies represented by his ex-law partner. Because of the price he'd already paid, the judges gave him only a fine and a suspended sentence. The sentence doesn't erase the guilty verdict.

The problem is that the other announced candidates of the center and left don't look like potential prime ministers. Kadima leader Shaul Mofaz lost all credibility by joining and quitting Netanyahu's government within 10 weeks. Labor leader Shelly Yacimovich has revived a dying party with her attacks on Netanyahu's robber-baron economics. But she's an ex-journalist who lacks the ministerial or military experience that Israeli voters expect. Yair Lapid, founder of a new centrist party, hasn't shown that he stands for much more than being Ashkenazi and secular. Former Kadima leader Tzipi Livni has yet to find a new party, enter the race, or demonstrated that she has the flexibility to pick up peace negotiations where Olmert left off.

The support for Olmert should be read as longing for a for  a plausible generic candidate who can make the case for negotiating peace. But in the course of the campaign, Olmert the idealist would not be able to free himself from Olmert the sleaze. The missing figure in Israeli politics is someone who can take the place of the crook.