Former Massachusetts Gov. Mitt Romney has emerged as the (for now) favorite to be John McCain's running mate, according to a report in Politico. Other favorites include former Rep. Rob Portman of Ohio and Sen. John Thune of South Dakota, with former Pennsylvania Gov. Tom Ridge, current Govs. Charlie Crist of Florida and Tim Pawlenty of Minnesota, and Rep. Eric Cantor of Virginia rounding out the shortlist. (Sen. Joe Lieberman, the Connecticut independent who was Al Gore's running mate in 2000, is also mentioned.) Whom should McCain select as his running mate, and why? Post your thoughts below.