Ms. Butler, who was appointed by Gov. Gavin Newsom just weeks ago to fill Dianne Feinstein’s seat, said she had realized that “this is not the greatest use of my voice.”
Laphonza Butler, who was appointed less than three weeks ago to fill the Senate seat left vacant by Dianne Feinstein’s death, said on Thursday that she would not run next year for the office, clearing the way for an open race in California that features three Democratic congressional members and a former Major League Baseball star.
In an interview with The New York Times, Senator Butler said that she intended to be “the loudest, proudest champion of California” in the remaining months of her term, but that she had realized “this is not the greatest use of my voice.”
A longtime California labor leader and rising star in the state’s Democratic Party, Ms. Butler was the president of the political action committee Emily’s List when Gov. Gavin Newsom appointed her this month. The swift decision came days after Ms. Feinstein’s death, and after a promise by Mr. Newsom to name a Black woman to complete the senator’s term.
Ms. Butler, 44, is the second Black woman to represent California in the Senate, after Vice President Kamala Harris, and the first openly L.G.B.T.Q. senator from the state.
She said that after she took office this month, she gave more serious thought to her long-term career prospects and consulted more deeply with her wife and 9-year-old daughter.
She said no single event or concern had influenced her decision, and she did not rule out a future run for elective office. Many in California Democratic circles said she would have been a formidable candidate, despite the relatively short time to build a campaign before the primary in March, and name recognition in the nation’s most populous state.
“I know it’s surprising — folks don’t traditionally see people who have power let it go, but this is a moment where I’ve had to mind my own truth and hold it in my own heart,” she said.
Californians will still have a wealth of candidates to choose from. Three high-profile Democratic members of Congress — Representatives Katie Porter, Adam Schiff and Barbara Lee — had been campaigning for months when Senator Feinstein died at 90 in late September. Steve Garvey, the former first baseman for the Los Angeles Dodgers and San Diego Padres, has also announced his candidacy as a Republican.
Several other Democrats, including Lexi Reese, a business executive from Silicon Valley, and Christina Pascucci, a Los Angeles newscaster, have also entered the race. So has Eric Early, a conservative Republican who has run unsuccessfully for Congress and state attorney general.
Mr. Schiff, who has the support of Nancy Pelosi, the former House speaker has amassed more than $30 million in cash, according to his most recent campaign filing, and polls have consistently shown him and Ms. Porter in the lead.
Ms. Butler said on Thursday that she had not yet decided whether to endorse anyone in next year’s Senate race.
“I haven’t thought about it much,” she said. “I have a great deal of respect for all the people who are running but I haven’t made any decisions yet.”
Ms. Butler spent nearly two decades at the Service Employees International Union, where she led a branch in California representing some 325,000 home-care workers. Her accomplishments included leading the fight for a $15 minimum wage in the state. Before taking the Senate appointment, Ms. Butler helmed Emily’s List, a powerhouse organization that helps Democratic women in favor of abortion rights get elected.
She also worked for a political consulting firm, where she advised Vice President Harris, Governor Newsom and the ride-share company Uber. She later was in charge of political advocacy at Airbnb.
Her appointment was politically complex for Mr. Newsom. Black members of Congress had mounted a campaign to persuade the governor to appoint Representative Lee, a longtime Bay Area congresswoman who is Black. They were upset in September when Mr. Newsom told NBC News that if Senator Feinstein had left office early, he would appoint a Black woman who would only serve on an interim basis.
After Ms. Feinstein’s death, Mr. Newsom shifted course and said that Ms. Butler could run for the seat in 2024 if she wanted to. Black leaders, including Representative Lee, praised his selection.
On Thursday, Aimee Allison, the founder of She the People, an organization that helps elect women of color, urged Ms. Butler to endorse Representative Lee.
“I applaud Senator Butler’s decision and look forward to working with her in the coming year,” Ms. Allison said in a statement. “She has the opportunity to be — once again — a queenmaker, this time for the next senator of California.”
Senator Butler said on Thursday that she was moved by the heady aftermath following her appointment. But, she said, in the ensuing days — including several spent in quarantine after she tested positive for Covid-19 — she discovered that “there are lots of ways for you to serve and to be of service.”
“I think I’m a typical millennial Gen-Xer who wants to offer my time and talents in ways that best speak to me,” she said. “Just because you can win a campaign doesn’t always mean you should run a campaign.”