At least according to Dan Riehl at Riehl world view who recalls an old Sullivan Post per election concerning Barack Obama:
On October 27, 2008, Andrew Sullivan posted: The Top Ten Reasons Conservatives Should Vote For Obama. Given all this playing out today, I thought I’d go back and have a look.
It’s high comedy but let me explain something. It’s my opinion Sullivan’s turn on Bush had everything to do with Bush’s position on Gay Marriage, it was after that point where Sullivan really started changing his tune and it was the (likely correct) belief that Obama was paying lip service to actual marriage during the campaign that made the difference in the other direction.
But as Glenn Reynolds points out the rubes are self identifying, but never fear. As soon a there is an actual Republican challenger to Obama all of our friends on the left who are beating their breasts today will support him, Mendoza line or no.
Update: Stacy Links and comments seem to agree with my Sullivan assessment, Oh and BTW the Mendoza line is a baseball term referring to hitting .200.