Sen. Barbara BoxerBarbara BoxerCarly Fiorina 'certainly looking at' Virginia Senate run Top Obama adviser signs with Hollywood talent agency: report Democrats vie for chance to take on Trump as California governor MORE (D-Calif.) will retire after finishing her current term in Congress, she announced on her website Thursday morning.
Boxer is 74 years old, and speculation that she would retire has been brewing for years, fueled recently by her stagnant fundraising. But she insisted that her age doesn't play a role in her decision.
"I feel as young as I did when I got elected," she said.
The senator's decision to retire ends a three-decade congressional career and leaves the Senate without one of its strongest liberal voices on environmental issues. Her decision will also open up the top Democratic spot on the Environment and Public Works Committee, which she chaired last Congress.
President Obama, who spoke to Boxer by phone while traveling on Thursday, hailed the California lawmaker as a Senate “institution.”
“She’s served the people of California for more than three decades with distinction, fighting for the issues that are close to their homes and hearts,” Obama said.
Vice President Biden, who worked alongside Boxer for decades, said she had “been my soul mate in the Senate for a long time.”
“You always knew in the Senate if you had Barbara on your side, you didn’t need much more,” Biden said, noting their collaborative efforts on environmental legislation and the Violence Against Women Act. “I am sorry to see her go, but there are still two years left.”
House Minority Leader Nancy Pelosi (D-Calif.), a close ally, appeared stunned when she was told of the news during a Thursday morning press conference.
"That's funny, she called me, said she wanted to talk personally. I thought she maybe wanted to have dinner tonight or something," Pelosi said.
"Her decision is an important one for her and her family — it's all personal and individual. Sen. Boxer has been such a champion for the people of California and indeed for our entire country," she continued, calling Boxer's exit "a real loss" for their state and for Congress.
Boxer's decision means California will have an open seat for the first time in more than two decades, potentially breaking a logjam of ambition for rising Democratic stars in the state.
Potential candidates include California Attorney General Kamala Harris (D) and California Lt. Gov. Gavin Newsom (D), two rising national stars in the party.
However, one might decide to wait for an open gubernatorial seat or to see whether Sen. Dianne Feinstein (D-Calif.) retires after her term — Harris and Newsom share advisers and have been working to tamp down the appearance of a conflict.
A number of other Democrats have been said to be quietly mulling runs should Boxer retire, including billionaire environmentalist Tom Steyer, Los Angeles Mayor Eric Garcetti (D), former Los Angeles Mayor Antonio Villaraigosa (D), and Reps. Jackie Speier (D-Calif.) and Raul Ruiz (D-Calif.).
California's unusual nonpartisan "jungle" primary could further complicate the race, making it more expensive and increasing candidate interest. The top two vote-getters, regardless of party, advance to the general election.
Republicans might seek to compete for the open seat as well, even though California has proven to be tough to crack for any GOP candidates in the last decade. Former HP CEO Carly Fiorina (R), who lost to Boxer in 2010 and is moving toward a presidential campaign, is already ruling out another run for the seat — her spokeswoman tweeted out that Fiorina "is a resident of Virginia and has been for years."
Republicans have also mentioned former Treasury official Neel Kashkari (R), who ran for governor in 2014. Sources close to Rep. Darrel Issa (R-Calif.) signaled Thursday he wasn't interested in a bid.
National Republicans argued Boxer's decision was due to the party's losses, predicting there would be more exits to come.
"This could be the first of many Senate retirements thanks to their new Democrat minority status. Today’s news raises the question whether there will be additional Democrat Senate retirements on the horizon," said National Republican Senatorial Committee spokeswoman Andrea Bozek. "Senate Democrats are already $20 million in debt and Senator Boxer’s retirement can’t be welcome news for the DSCC who has to defend a costly and hotly contested open seat.”
Democratic Senatorial Campaign Committee Chairman Jon Tester (Mont.) called Boxer a "fearless and dedicated legislator" in a statement, expressing confidence they would keep the seat.
"I appreciate that Senator Boxer has made an early decision, giving us more than enough time to get behind a strong Democratic candidate who will hold this seat," said Tester. "We’re confident that in November 2016 we will elect a new Democratic senator who will carry on Barbara Boxer's proud tradition of fighting for California."
— Mike Lillis contributed.
— This story was last updated at 1:25 p.m.