America’s most populous state will have a contested Senate race next year, the first since the state’s attorney general at the time, Kamala Harris, swept the field in 2016. It sets up a clash between various factions of the Democratic Party for a seat that could be held by the winner for decades. 

The incumbent, Senator Feinstein, has served in the upper chamber for more than 30 years, and will turn 90 this summer. Concerns about Ms. Feinstein’s mental faculties have risen in recent years, to the point that many political observers believe she will not seek a seventh term. She raised $558 in the last three months, and has only around $10,000 in the bank. Other candidates, meanwhile, are raking in millions of dollars. 

That clears the field for what will be a hotly contested intraparty fight among the Democrats. California adopted a “jungle primary” system in 2008, meaning that all candidates from every party run in the same primary, with the top two vote getters moving on to the general election. This means two high-profile Democrats could be battling for the seat in November 2024. Several candidates have either declared their candidacies, told colleagues about their plans, or publicly expressed a desire to run. 

Last week, Congressman Adam Schiff, a longtime, high-profile figure in the Democrats’ fight against President Trump, announced his candidacy in a campaign video posted to Twitter. Mr. Schiff’s message focused solely on his anti-Trump bona fides.  

He also received a conditional endorsement on Thursday from Speaker Pelosi, who said in a statement that she would support Mr. Schiff should Ms. Feinstein decide to retire. 

He has proven to be a prolific fundraiser, bringing in millions of dollars for the party since his ascension to chief investigator of Mr. Trump. 

Mr. Schiff was recently removed from the House Intelligence Committee by Speaker McCarthy, who said Mr. Schiff’s chairmanship of the committee “severely undermined its primary national security and oversight missions.” 

In response, Mr. Schiff said Mr. McCarthy “will soon find out just how wrong he is” in assuming Mr. Schiff will go quietly. The Los Angeles congressman has sent out several fundraising emails since the speaker’s announcement.  

The first candidate to officially enter the race was Congresswoman Katie Porter, an avowed progressive, social media star, and protege of Senator Warren. Ms. Porter was first elected to Congress in 2018 in a traditionally Republican seat based in Orange County. Ms. Porter was criticized for the timing of her announcement, however.

Jessica Taylor of the Cook Political Report wrote that “for someone looking to represent the entire state, her timing wasn’t particularly savvy, coming as much of the state was facing devastating storms and flooding.”

Ms. Porter raised $1.3 million in the hours following her announcement. Like Mr. Schiff, she has proven to be one of the most prolific money-makers in Congress. By the end of the 2022 midterm cycle, Ms. Porter had raised a combined total of $25.4 million — just ahead of Ms. Pelosi and just behind Mr. McCarthy. 

Ms. Porter’s ties to the progressive movement are deep. She first became famous on social media in 2019 when she grilled bank executives during a series of congressional oversight hearings, bashing the C-suite men for their compensation and corporate practices. Ms. Porter also won praise for running — and winning — in a swing district while supporting Medicare-for-All. 

While a student at Harvard Law School, Ms. Porter became close with Elizabeth Warren, who was then a professor. Ms. Warren tapped Ms. Porter to serve as her presidential campaign co-chairwoman, and has now endorsed Ms. Porter’s Senate campaign. 

A recent poll from the firm David Binder Research has Ms. Porter leading Mr. Schiff in the primary by 37 percent to 26 percent. 

Another candidate who reportedly told colleagues of her intention to run is Congresswoman Barbara Lee, who has represented the city of Oakland in the House since the 1990s. She became famous for being the only member of either the House or the Senate to vote against the 2001 authorization for use of military force in Afghanistan. 

“I rise today with a very heavy heart,” she said in a floor speech at the time. “September 11th changed the world. Our deepest fears now haunt us. Yet I am convinced that military action will not prevent further action of international terrorism against the United States.”

“As we act, let us not become the evil that we deplore,” she said. 

Ms. Lee told members of the Congressional Black Caucus she would run for the Senate, according to Politico. She would be the only major African-American candidate to run, which would help in a state known for its traditional north-south divide. 

One could also expect Ms. Lee to be appointed to the seat should Ms. Feinstein retire early. Governor Newsom pledged to appoint an African-American woman to the seat if given the opportunity, and as one of California’s longest-serving lawmakers, Ms. Lee would be on Mr. Newsom’s shortlist. 

Ms. Taylor of the Cook Political Report notes that a senator’s individual power comes from decades in the chamber, forging relationships and institutional experience.

“Lee would also be 78 come Election Day and wouldn’t have the chance to amass decades of seniority like other younger challengers might,” Ms. Taylor wrote. “Anticipating such an argument, the San Francisco Chronicle reported her advisers are pitching her as a transitional candidate who would serve just one term.” 

California has a long history of electing senators to serve for decades on end. Ms. Feinstein and Senator Boxer dominated the state through the presidencies of Bill Clinton, George W. Bush, Barack Obama, and Donald Trump. The state’s junior senator, Alex Padilla, is 49 — meaning he could be in that seat for 30 or 40 years.

Ms. Feinstein’s potential retirement may be the only hope for ambitious, young California politicians to take a run for the U.S. Senate.