For some reason, Republican candidates and other conservatives have consistantly talked about their party as being a stool made of three legs: economic conservatives (tax cuts are a panacea and social darwinism), foreign policy conservatives (Iraq went so well, let's bomb Iran too), and social conservatives (pro-life, anti-gay, culture warrior). Each of the three candidates remaining before Super Tuesday represented these "legs" --Romney is first and foremost a economic conservative, wanting tax cuts for the rich and spending cuts on social programs; McCain is the neocon: author of the surge and ur-supporter of the Iraq war, his key senatorial endorsees are Iraq war cheerleaders Linsay Graham and Joe Lieberman; and Huckabee is the social conservative...an ordianed Baptist minister no less. Now there was overlap, Romney lead on the issue of Gay Marriage when his state's supreme court legalized it and McCain has supported tax cuts in the past.
This weekend's Conservative PAC meeting in DC (CPAC) really shows the possiblity that the Republican party's base would rather be right than win. John McCain got booed, Romney was begged not to quit, and Ann Coulter tried to garner attention by claiming to support Hillary Clinton over McCain (her books didn't sell this year at CPAC though).
John McCain's speech was well recieved, but conservatives feel about him the way Democrats feel about Joe Lieberman--betrayed. It appears that while Clinton and Obama campaign for at least another month, McCain is going to have to assusage conservative fears by promising to do very conservative things very explicitly. It is another month that John McCain can't fundraise and organize his team for the fall, and another month he can't attack the Democratic nominee because there is basically a 50-50 chance either one of them could win.
It is up to the RNC and 527s to start hitting Obama and Clinton hard for him, but given his campaign finance reform stance, he can't really let the 527s to that for him, so that leaves the Party. Then he has the problem of tarnishing his "Maverick" image that gives him good numbers among swing voters. The more he has to shout "I'm just like George Bush!" from the hilltops, the more problematic it is for him.
Meanwhile, Democratic 527s can start attacking McCain now and Clinton and Obama will have a reasonable case to be made that they had nothing to do with it. They can show pictures of McCain hugging Bush, and Bush and McCain celebrating his birthday while New Orleans drowned. Democrats are clearly going to try to merge McCain into Bush, while McCain feels the need to do the same to shore up his base.