From today's Washington Post, David Broder writes the following:
Virginia was part of President Bush's sweep of Dixie last November, when the South also elected five new Republican senators to formerly Democratic seats. The Kaine-Kilgore race will signal whether the momentum of those victories continues. Should Warner be able to help Kaine keep the governorship in Democratic hands, it would enhance Warner's growing reputation as a potential aspirant for the 2008 national ticket. Warner has won plaudits as the current chairman of the National Governors Association, one of the steppingstones in Bill Clinton's rise to the presidency. But he needs to demonstrate, through a successful effort for Kaine, that he was more than a brief deviation in Virginia's Republicanism.On the other side, Kilgore has the backing of the state's former Republican governor, Sen. George Allen, a personable conservative campaigner who built his national reputation as last year's successful chairman of the National Republican Senatorial Committee. A Kilgore victory would be another feather in Allen's 2008 cap.
In other words, helping Kaine this year helps Mark Warner while hurting George Allen. Reason #5,872 to "Raise Kaine" this year in Virginia.