This isn't exactly the sort of news that reassures conservatives that the GOP's nominee isn't so bad after all,

ABC News' Teddy Davis Reports: On Wednesday, a top adviser to John McCain said more definitively than he has in the past 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.

"I would simply be uncomfortable being in a campaign that would be inevitably attacking Barack Obama," said McCain adviser Mark McKinnon in an interview with NPR's "All Things Considered." "I think it would be uncomfortable for me, and I think it would be bad for the McCain campaign."

McKinnon, who was a Democrat before serving as President Bush's ad maker in 2000 and 2004, said that he plans to be behind McCain "100 percent" no matter who the Democratic nominee is. He explained, however, that if the Democrats nominate Obama, he will be supporting McCain "from the sidelines."

While saying that he does not agree with Obama on every issue, McKinnon gushed about the Illinois Democrat.

The fact that John McCain has guys on his staff like Mark McKinnon, who's "gushing" over the most liberal man in the Senate and Juan Hernandez, whose loyalty is to Mexico first and America 2nd, is disturbing.

Granted, McCain is, well, McCain -- essentially a Scoop Jackson Democrat with a "R" beside of his name. However, he is going to need the support of conservatives to win in 2008 and jettisoning staffers like McKinnon and Hernandez from his campaign should be a no-brainer at this point. Why have people on your staff whose very presence makes conservatives deeply and rightly suspicious of you?

Moreover, even if McCain could somehow win the election without getting solid support from the Right, which is unlikely, he's going to have to start meeting conservatives halfway on a few issues to build up some good will or he's not going to be able to accomplish anything even if he's elected. If he becomes the President of the United States, the Democrats are going to oppose McCain on most things reflexively and if say, half his own party is fighting him on everything, too, he's going to be hamstrung from the very beginning of his presidency -- which honestly, given McCain's record, might not be the worst thing in the world for the Republican Party.