Democrats have a supremely deep bench of possible successors, along with some dark horses. The 2016 race also will be a test for whether Republicans can regain a Senate seat in the Golden State, which has eluded them since 1992.
Here’s an updated look at some of the possibilities, broken down by party and the person’s candidacy status:
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Attorney General Kamala Harris: Harris announced Jan. 13 that she is running. She has recently been making the rounds in Washington and building her national profile, as well as fundraising and locking down endorsements across California. She could benefit from an expected Hillary Clinton presidential campaign in 2016.
Rep. Adam Schiff: The Burbank Democrat, elected in 2000, “has been encouraged by many Californians” to run for Boxer’s seat, he said. Schiff recently became the top Democrat on the House Intelligence Committee. He has emerged as a widely quoted expert on foreign affairs, yet it’s unknown how well that would help him in an expensive statewide race.
Rep. Xavier Becerra: The Los Angeles Democrat said he is taking “a very close look” at running for the Senate. Becerra has climbed the ranks in the House, where he has served since 1993, so a Senate campaign would necessitate giving up his comfortable position in Congress.
Rep. Loretta Sanchez: The Santa Ana Democrat, elected in 1997, could fulfill the Latino community’s desire to have a candidate in the race. She does not plan to announce her intentions for several more months. “This is not a decision I want to make in haste,” Sanchez said in January.
Rep. John Garamendi: The Walnut Grove Democrat indicated in January that he was weighing a run, but has made no formal announcements. Elected in 2009, Garamendi previously won statewide elections for lieutenant governor and insurance commissioner.
Former Los Angeles Mayor Antonio Villaraigosa: The former Assembly Speaker said Tuesday that he would pass and “instead continue my efforts to make California a better place to live, work and raise a family.” Villaraigosa has said he enjoys being a chief executive, suggesting he may seek the governorship in 2018.
Lt. Gov. Gavin Newsom: Newsom has the portfolio to compete for Boxer’s seat. But the former San Francisco mayor, who rose to prominence after legalizing gay marriage in the city in 2004, announced Jan. 12 that he will pass. He has formed a finance committee for governor in 2018.
Climate change activist Tom Steyer: The billionaire hedge fund manager said Jan. 22 that he will not run. Steyer spent $74 million, mostly unsuccessfully, trying to elect more environmentally friendly candidates in 2014.
Treasurer John Chiang: Chiang nixed a Senate run on Jan. 24, citing plans to focus on his new position. But as one of the most visible Asian Americans in a state where the rapidly growing population segment is increasingly flexing its political power, he could be a viable contender in future statewide contests.
Assemblyman Rocky Chávez: The Oceanside Republican formed an exploratory committee for a Senate run in February. Would predominantly Democrat Latino voters cross party lines to support his candidacy?
Former state GOP chairman Tom Del Beccaro: While acknowledging the difficulties that Republicans now face winning statewide office in California, Del Beccaro also formed an exploratory committee in February.
Former Rep. David Dreier: A longtime congressman from San Dimas, Dreier has been approached about a potential campaign, according to a spokesman.
Former state GOP chairman Duf Sundheim: In January, Sundheim expressed interest in potentially mounting a campaign, but he has been quiet since then.
Former U.S. Secretary of State Condoleezza Rice: A dream candidate for California Republicans, who have been wanting her to run for something – anything – for years. They’ll have to keep waiting. Rice has said the Senate is “not even a consideration,” even after she led a recent Field Poll of California voters.
Former U.S. Senate candidate Carly Fiorina: The former Hewlett-Packard CEO suffered a bruising loss to Boxer in 2010. Recently, Fiorina has been floating her name for a possible presidential run in 2016 instead.
San Diego Mayor Kevin Faulconer: As mayor of the second-biggest city in California, Faulconer has a platform but no statewide profile. He cut short speculation on Jan. 8, saying his “focus is on leading San Diego and continuing to write our city’s comeback story.”
Former gubernatorial candidate Neel Kashkari: After a massive loss to Gov. Jerry Brown in November, the former U.S. Treasury official ruled out a Senate run on Feb. 7.