Today Mitt Romney dropped out of the Republican race today, leaving McCain as the apparent nominee for that party. The Democratic race is still up for grabs with a long fight lying ahead.
I will go out on a limb and predict that McCain's only chance is that if Clinton becomes the Democratic nominee. I think this because Clinton is the only force that will motivate the conservatives in the Republican Party to vote in November. The conservatives are not overly thrilled with McCain, and will not be motivated to vote if Obama is the contender. Considering the razor thin margins of the recent presidential races, whichever party can maximize voter turnout, will take the presidency.
I still think that the democratic machine will back Clinton and that she will pull out the nomination. I believe that the long fought battle against Obama will drain her war chest substantially as well as enabling McCain start campaigning on a national level while the democrats are still fighting for the nomination. This will give McCain another advantage. I think that at the end of the day, that enough moderates will swing to McCain and join forces with the anti-Clinton motivated base will swing the election to McCain in November.