Mr. Newsom acknowledged in an interview on Wednesday that he had made a choice to be less outspoken on same-sex marriage compared with past years. He said his new tone reflected how the debate had matured and was not a sign that he had changed his commitment to the issue.

"This movement has nothing to do with me; I'm just a small part of it," Mr. Newsom said. "This thing is at a completely different level now. What we needed to do in 2004 was to put a human face on it, and I think we achieved that goal. Now let's take the politics and the politicians out of it."

Mr. Newsom's new strategy also appears to reflect a political calculation as he seeks statewide office for the first time. In the San Joaquin Valley and Southern California, large pockets of the electorate remain hostile to same-sex marriage. Even if his Republican opponent, Lt. Gov. Abel Maldonado, does not explicitly make an issue of it, there are signs that it will play an indirect part in the campaign as Mr. Maldonado seeks to portray Mr. Newsom as an out-of-touch San Francisco liberal.