San Francisco Mayor Gavin Newsom officially tossed his hat into the ring via Twitter and other social media sites on April 21.
Los Angeles Mayor Antonio Villaraigosa made it clear Monday that he won't run for the post in the next election.
"I can't leave this city in the middle of a crisis," Villaraigosa said on CNN. "I was elected and re-elected by the people of this city. I feel compelled to complete the promise I made to them."
The Democratic mayor appeared on CNN's "The Situation Room with Wolf Blitzer."
Villaraigosa said a month ago he would consider joining the campaign to replace Gov. Arnold Schwarzenegger, who is barred by law from seeking a third consecutive term. Typically, aspiring candidates for governor would begin aggressively raising money and making appearances around California, but the mayor has shown few signs that he is preparing for a statewide candidacy as he contends with a budget crisis and recession in his hometown.
When asked whether he would endorse a candidate, Villaraigosa said he is "not focused on that."
"There's plenty of time to weigh in on that race," he said.
Newsom will still have strong competition in other potential candidates including Attorney General Jerry Brown, also a Democrat, and several Republicans including former Rep. Tom Campbell, Insurance Commissioner Steve Poizner and former eBay chief executive Meg Whitman.