While I am not privy to internal campaign rumors, I have a good sense of whom McCain and Obama ought to choose as their vice-presidential nominees.
Republican: Bobby Jindal, Governor of Louisiana. There's speculation that McCain will choose Tim Pawlenty, the young Governor of Minnesota and one of McCain's early supporters in the dark days of his candidacy, or his buddy, Charlie Crist, the Governor of Florida. Both of these selections would be mistakes.
Running a ticket of two white men against Barack Obama would not be visually appealing - even more so if the Democratic V.P. nominee is female. It might appeal to the 20% of the electorate that won't vote for a black man, but it would marginalize the Republican ticket in the eyes of independent voters in key swing states.
Jindal is young, rising, and savvy, and he heralds a new role for Indian-Americans in U.S. politics. If McCain wins, he's in pole position to succeed him. If McCain loses, it's no skin off his back; Jindal can go back to being an effective governor and burnishing his credentials. Franklin D. Roosevelt wasn't hurt by running with James Cox (and losing badly) in 1920 when his turn came twelve years later.
Democratic: Ted Strickland, Governor of Ohio. Barack Obama won't, and shouldn't, choose Hillary Clinton. There's too much water under the bridge. When Senator Obama thanked Senator Clinton for making him a stronger candidate, he really meant, "Thanks for digging up all the dirt on me in the primaries, so that voters forget about it come November." Privately, he doesn't want the Clintons anywhere near the ticket. He has enough to worry about.
But he does have to worry about the Electoral College. McCain will win Florida - older voters tend to care more about Obama's race than younger voters. Obama has an uphill climb in Ohio, which Kerry narrowly lost in 2004, and Pennsylvania, where Hillary decisively beat him. Even if he can turn Virginia, Colorado, and New Mexico, he needs one of those two states.
Strickland is his best bet to carry Ohio and appeal to Appalachia in general - he studied at Kentucky's well-reputed Asbury Theological Seminary, earning an M. Div., and has a doctorate from the University of Kentucky. He would be a potent ally for Obama, and has the advantage of starting the primary season as a Hillary supporter.