The effect a nominee's running mate has on the election is uncertain - LBJ clearly helped Kennedy in the south, but in truth, the running mate probably has little impact.

Nevertheless, who a nominee chooses is important for various reasons.  It shows a nominee's judgment, both political and substantive.  A future VP is, by the nature of the office, a potential future president.  Furthermore, a nominee's choice in VP potentially shows the direction the nominee wants to take his or her party.

Not always.  Joe Lieberman was a purely political choice by Al Gore that might have paid off if it weren't for those confounded butterfly matters.  Dick Cheney was an establishment choice with no ambition.  Al Gore, on the other hand, did symbolize the kind of Democrat Bill Clinton wanted to see running for high office.

Barack Obama doesn't have to cultivate, say, an "Obama Democrat" who will conform to the desires and leadership of the top of the ticket.  Obama already is the future of the party.  He'd be better off selecting a less visible and more managerially competent running mate with sharp political instincts.  I have long supported Chris Dodd in this regard.

McCain, on the other hand, has a vested interest in influencing the party's future.  Who he chooses as his running mate could determine the future direction of the GOP.  He is probably being pressured to choose a base-pleaser such as Minnesota Gov. Tim Pawlenty or, yikes, Mike Huckabee.  Mitt Romney could fulfill this role and any other role possible if the winds dictate.

In my view, Romney would have been an ideal choice had he stuck to his moderate principles, but he didn't.  If McCain really wnats to moderate the GOP's image and ensure the party's future viability, he needs to annoint someone who appeals beyond the base.

The ideal candidate, in my view, is Michigan Congressman Fred Upton.  Unlike the Norquistians - who currently have a Vulcan death grip on Republican tax policy - Upton has a broader view of government, generally favoring limited government but conceding the crucial point that government can accomplish positive good.  Bush's "compassionate conservatism," believe it or not, did politically succeed, only to fail as he tried to paradoxically export it via military force.  That kind of conservatism, of course, was largely a creature of the right.  Upton's brand is a product of the center.

If McCain wants to win, he needs to play to his strengths and go for the political center.  Besides, reaching for Michigan's 17 electoral points probably has lower risk and obviously has greater potential reward than trying to win other northern midwestern states like Minnesota or Wisconsin.

Sadly, McCain probably won't move the Republican Party to the center, and he has already betrayed his moderate principles in favor of George W. Bush's approach wholesale.  The upside is that this makes the future political success of the Democratic Party all the more likely.