If Virginia's Kaine were picked, the lieutenant governor is Bill Bolling, a Republican, giving the GOP control of the governor's mansion for the first time since 2002.
Arizona doesn't have a lieutenant governor, so Secretary of State Jan Brewer, a Republican, would take over if Napolitano were tapped, giving the GOP the reins of power in both the Legislature and the governor's office.
Montana Lt. Gov. John Bohlinger, a Republican, would take over for Schweitzer, whose win in 2004 put a Democrat in the governor's office for the first time since 1989. (Montana is the only state with a Democrat and Republican voluntarily on the same ticket.)
In Kansas, Lt. Gov. Mark Parkinson switched to the Democratic Party in 2006 after serving four years as Republican Party Chairman and as a Republican state legislator during the 1990s, so his ascension would put his party leanings to the test.
When Senators are considered for the VP nod, people routinely ask whether their governors are from the same party as them. Democratic Senator Evan Bayh, for example, is a tricky VP pick for Obama because Indiana has a Republican governor who would likely fill Bayh's vacated seat with a Republican. Jeopardizing a 60-seat majority is a major no-no.
The party affiliation of lieutenant governors is a lot less important, but probably worth more attention than it gets.