The state Supreme Court's decision to uphold California's constitutional ban on gay marriage — and the prospect that an impassioned initiative to overturn it could share the ballot with next year's governor's race — holds consequences for candidates from both parties, but especially for the one most deeply associated with the issue.

The intensity of a statewide vote on same-sex marriage could make it difficult for Newsom to connect with centrist voters, millions of whom voted no on the issue last year.

"It certainly underlines Gavin Newsom's previous advocacy for same-sex marriage. I think that might be a two-edged sword for him," said Mark DiCamillo, director of the San Francisco-based Field Poll.

Other possible Democratic contenders including Attorney General Jerry Brown, Los Angeles Mayor Antonio Villaraigosa and Lt. Gov. John Garamendi also support same-sex marriage. So does one of the three leading Republican hopefuls, former U.S. Rep. Tom Campbell, but former eBay chief executive Meg Whitman and state Insurance Commissioner Steve Poizner oppose it.