Today brought the news that former Massachusetts Governor Bill Weld (and Mitt Romney booster in the '08 GOP primaries) is endorsing Obama. He joins Colin Powell, Arne Carlson, Ken Adelman, and Scott McClellan in defecting from the GOP to Obama.

So who's next? I can't imagine an actual Republican office holder--even one in danger of getting swept away by a blue wave, like Gordon Smith in Oregon--will take the plunge (although Smith, of course, has stopped just short of endorsing Obama).

Turning to the formers, the has-beens, and (in McClellan's case) the never-wases, I was thinking Michael Brown might be a good candidate. But, as I see from his blog (yes, Brownie has a blog), he was disappointed that Colin Powell endorsed at all, so I'm guessing Brown will keep his powder dry. Tom Kean--sort of Bill Weld's alter ego--seems pretty squarely in McCain's corner. But I'd keep an eye on George Pataki, who endorsed McCain in February but seems to have been AWOL of late.

So that's my best guess: Pataki. Put your best guesses in TalkBack.

Update: Damn, I should have guessed Charles Fried!

--Jason Zengerle