In a vacuum, these might be plausible constituencies for Hizzoner — but not in an election where Sarah Palin is the Republican nominee! How many northeastern progressives (or Lincoln Chafee Republicans, for that matter) would contemplate casting a vote for a third-party candidate knowing that it might deliver the White House to the woman they fear and loathe above all others? Not many, I’d say. Nothing would be guaranteed to rally the Obama coalition quite like the specter of a Palin presidency: For months before the election, the drumbeat that “a vote for Bloomberg is a vote for Palin” would be well-nigh deafening, and I’m pretty sure that even a weakened Obama wouldn’t have that much trouble holding serve in that scenario, relegating Bloomberg to exactly the kind of John Anderson-esque performance that would be his most likely fate in any case.