I think there is definitely room for a third-party candidacy in 2008, but I don’t think Bloomy is the right guy to fill that void. Any successful independent candidate needs to appeal to those disaffected voters whose views are generally to the right or center-right on fiscal issues but center-left on social issues: i.e., generally small-government, federalist/libertarian-ish folks. Those voters, on both sides of the aisle, are the ones who feel the most alienated by the two parties right now, IMHO. And I think most of them will react to Bloomberg the same way Glenn Reynolds does: “I’d like to see a third-party candidate, but I’d like one who stands for more freedom, not less, and the nannyish Lee Kuan Yew-wannabe Bloomberg clearly doesn’t fit that description.”
Maybe Bloomberg can position himself as a staunch states-rights (and cities-rights) guy, arguing that our federalist system leaves plenty of room for both types of state and local officials: the ones who are nannyish, and the ones who are more hands-off. In other words, maybe he can take the edge off his history of nannyism by convincing people that although he was a nannyish mayor, he wouldn’t be a nannyish president because he respects federalism. But I doubt that would work, even if it’s true (which I have no reason to believe it is).
P.S. Admittedly, maybe the reason I think an independent candidate needs to appeal to the demographic I described is because I’m a member of that demographic. :) But I don’t think so. I think that loosely described group — which is also mostly hawkish and generally tough on immigration — is the most susceptible of any large ideological group (other than the far left- and right-wing fringes, who aren’t large enough by themselves to support a serious, non-Nader/Buchanan-ish third-party candidacy) to the siren song of an independent candidate. I mean, what’s the alternative, really? If Bloomberg runs as liberal on social issues and nannyish on economic/regulatory issues, doesn’t that make him… a Democrat?