Karl Roves cites three possible affects of the prolonged Democrat nomination process on John McCain's chances: 1. Clinton and Obama bloody each other, leaving the Democrats with a "damaged goods" candidate for the general election.
2. The excitement of a brokered convention draws millions of sideliners into the political process, mostly on the Democrat side, giving whoever wins that party's nomination a leg up.
3. The protracted race pushes McCain off the front pages, allowing the Democrats to define McCain in any light they choose.
I say 2 and 3 are aspects of the same effect. Therefore, only two outcomes are possible: McCain wins or McCain loses.
How McCain Wins
Clinton Inc. will try to destroy Obama. They will pull out more trash than even I will. They will spin every utterance and past activity from Obama as a sinister plot by the junior Senator to overthrow the world. Instead of Daffy and Bugs, it'll be Pinky and the Brain. Press scrutiny of Obama, and Obama's decidedly poor handling of confrontation, dulls the shine on the "new messiah." Clinton shine was dulled years ago.
Under this scenario, if Obama wins the nomination, Clinton supporter (many) defect to McCain because Obama is too wimpy and pacifistic. McCain wins.
If Hillary gets the nod, disaffected Obama worshipers drop out of the political arena. They already equate Hillary with McCain as Washington insiders who represent big corporations. If Clinton wins, they'll cry foul, particularly if she does with Florida and Michigan wins. Conspiracy theories will run amock, and they'll be right.
How McCain Loses
Clinton and Obama rise above the tendancy to destroy each others' character. McCain can't buy space in a major news outlet, and disappears until the convention. In a civil convention, the SuperDelegates choose the party's nominee based on electability.
If the nominee is Obama, the messiah march continues right up to a popular and electoral landslide of the Reaganesque proportions.
If Hillary is the nominee, a tough battle with McCain goes to the Dems in a close race decided on "he's too old" or "he's the past."
McCain has more influence than some think. By being outlandishly conservative, getting Phil Gramm and Jack Kemp out front, and spending lots on television, he can keep his name in the paper, energize the conservative base, and reach people who are getting sick of the Democrats.
Clinton will savage Obama, and Obama won't handle scrutiny well. Obama might still win the nomination, but he'll truly be damaged goods. McCain will have to run the perfect campaign, but he can beat Obama.
If Clinton wins, she'll be seen as a shrew. Obama's support is NOT political, it's religious. So his followers will abandon politics (at least 30 percent will, anyway). Without them, McCain wins in a cake walk.
Bottom Line: Barring some unforseen event, Hillary cannot win the White House, McCain probably won't, and the race is Obama's to lose.
UPDATE: Ed Morrissey and Andrew Sullivan have the same take on Obama's supporters as I do.