Via Brian Beutler, a pretty odd story from the heart of the McCain campaign:

A top adviser to John McCain said Wednesday that he will step down from the Arizona senator's presidential campaign if the presumed GOP nominee faces Sen. Barack Obama, D-Ill., in the general election.

McKinnon was a Texas Democrat who started working for George W. Bush in the late-1990s before becoming one of the early wave of Bush-affiliated political hacks to sign on with McCain 2008 before the campaign's temporary collapse. He's also been talkingup Obama for some time. Here he is in December 2006:

Mark McKinnon, who was a top adviser to President Bush in his two White House runs and who is a senior adviser to Senator John McCain, Republican of Arizona and a likely presidential candidate in 2008, said, “I think Barack Obama is the most interesting persona to appear on the political radar screen in decades.” He added, “He’s a walking, talking hope machine, and he may reshape American politics.”

A walking, talking hope machine sounds a bit frightening to me, but I think that was meant as praise.