In the race for the presidency, having served as a governor is a big resume boost. Among recent occupants of the White House, look at President George W. Bush (Texas) and predecessors Bill Clinton (Arkansas), and Ronald Reagan (California)—all ex-CEOs of their states.

In this presidential campaign, there are two ex-governors running for office — Republicans Mitt Romney, of Massachusetts, and Mike Huckabee, of Arkansas. And, on the Democratic side, New Mexico Gov. Bill Richardson is seeking the nation’s highest office while remaining his state’s chief executive.

But if you can’t be a governor, you’d better round ‘em up in your camp. Governors can often help deliver precious electoral votes from their states. In return, governors can be considered for cabinet posts (think former Pennsylvania Gov. Tom Ridge, who went on to head homeland security under Bush), or as a possible vice-presidential pick.

Among the pack of non-governors running for president this year, two U.S. Senators--Democrat Hillary Clinton and Republican John McCain--have lined up the most gubernatorial endorsements, according to a list of who’s endorsing who compiled by Stateline.org.

Here’s the list of Democratic governors supporting Sen. Clinton, of New York: Her own state’s governor, Eliot Spitzer, along with Govs. Mike Beebe, of Arkansas, Martin O’Malley, of Maryland, Ted Strickland, of Ohio, John Baldacci, of Maine, Jennifer Granholm, of Michigan, Jon Corzine, of New Jersey, and Ted Kulongoski, of Oregon.

Sen. McCain, of Arizona, doesn’t get the nod of his own governor (Janet Napolitano is a Democrat), but does get the support of Republicans Tim Pawlenty, of Minnesota, (whose name has been kicked around as a possible VP pick), Jon Huntsman, of Utah, Mitch Daniels, of Indiana, and Jim Douglas, of Vermont.

On Democratic Sen. Barack Obama’s side are Rod Blagojevich, of Illinois (Obama’s governor), Tim Kaine, of Virginia, Deval Patrick, of Massachusetts, and Jim Doyle, of Wisconsin.

Republican Mike Huckabee, the resounding GOP choice for Iowa caucus-goers, gets just one endorsement—from South Dakota Gov. Mike Rounds, who must have sensed something few others did when he endorsed the little-known Arkansas ex-governor way back in April. (South Dakota has a mere three electoral votes.)

Three GOP governors line up behind Romney: Missouri’s Matt Blunt, (who, by most accounts, is facing a tough re-election race in his own state), Nebraska’s Dave Heineman, and Rhode Island’s Don Carcieri.

And last but not least, former New York City Mayor Rudy Giuiliani picks up Texas Gov. Rick Perry’s support.

JAN. 9 UPDATE: Now that Delaware Sen. Joe Biden, a Democrat, has dropped his bid for the nomination, and now that Sen. Hillary Clinton of New York has won New Hampshire, Delaware Gov. Ruth Ann Minner has jumped on the Hillary bandwagon.

JAN. 11 UPDATE: The Washington Post’s The Fix blog is reporting that Napolitano, the former chair of the National Governors Association who made innovation in education her NGA platform, is supporting Obama.