By Sharon Bernstein
SACRAMENTO, Calif. (Reuters) - California Lieutenant Governor Gavin Newsom, whose support for same-sex marriage while mayor of San Francisco kicked off a tidal wave of social and political change, said on Monday he would not run to replace retiring U.S. Senator Barbara Boxer in 2016.
Newsom's decision leaves the field wide open for a growing host of potential candidates, among them California Attorney General Kamala Harris and former Los Angeles Mayor Antonio Villaraigosa, both Democrats.
"...My head and my heart, my young family's future, and our unfinished work all remain firmly in the State of California - not Washington, D.C.," Newsom wrote on his Facebook page on Monday morning.
Boxer's departure when her term ends in 2016, announced last week, is the first of three anticipated retirements among California's top leaders that should open up room for a younger generation of politicians who have been waiting in the wings for decades.
Governor Jerry Brown, 76, will have to leave office when his fourth term ends in 2018 because of term limits. U.S. Senator Dianne Feinstein, 81, will be 85 when her term ends.
Newsom, 47, is viewed by some close to him as inclined to think more like a chief executive than a legislator, and is widely believed to be pondering a gubernatorial run when Brown leaves office.
Harris, 50, who like Newsom hails from the San Francisco political scene, is a former district attorney who has used her position to develop policy ideas as well as handle prosecutions.
The state capital was abuzz with speculation on Monday evening that Harris would soon announce her candidacy. The Los Angeles Times, citing an anonymous Harris adviser, reported on its website on Monday that she would announce her campaign for Senate on Tuesday.
Harris has been notably silent on her ambitions but has been frequently mentioned as a candidate for either the U.S. Senate or for governor.
Of African-American and South Asian descent, she is the daughter of two college professors and grew up during the civil rights turmoil of the 1960s in the Bay Area.
Villaraigosa used Facebook over the weekend to announce that he was seriously considering running to replace Boxer.
Others considering running include environmentalist Tom Steyer, a Democrat. Republican candidates have not yet emerged, although the Los Angeles Times reported that Assemblyman Rocky Chavez and two former state party chairmen are considering bids.