(CNN) - Former President Bill Clinton will endorse San Francisco mayor Gavin Newsom in the 2010 California governor's race, a Clinton aide confirmed to CNN.
Clinton's decision to weigh in for Newsom puts him at odds once again with the candidate many consider the likely frontrunner for the Democratic nomination - California Attorney General and former governor Jerry Brown, the man Clinton defeated for the 1992 Democratic presidential nomination.
But Newsom curried favor with the former president in 2008, when he endorsed and campaigned actively for Hillary Clinton during her quest for the Democratic presidential nomination. The 42nd president is now returning the favor by throwing his weight around in a Democratic primary, as he has done with other 2010 candidates who backed Hillary's bid last year.
Clinton has endorsed Florida Rep. Kendrick Meek and Ohio Lt. Gov. Lee Fisher in their 2010 Senate bids, even though both candidates have yet to secure their party's nomination. He also backed his longtime ally Terry McAuliffe in the Virginia governor's race, but McAuliffe lost a three-way fight for the Democratic nomination in June.
The endorsement was first reported by ABC News.