Voters will see the Senate election twice on the March primary ballot: the regularly scheduled election for the six-year Senate term that begins in 2025, and a special election to select a replacement to serve out the remainder of the late Sen. Dianne Feinstein’s term, which ends in January. In November, voters will be asked to choose between the top two candidates in both races.

The quadruple ballot could introduce a note of chaos into the competitive Senate primary, which already has a crowded field of candidates. More than 30 people have filed to run for the six-year term that ends in 2031, including U.S. Reps. Adam Schiff (D-Burbank), Katie Porter (D-Irvine) and Barbara Lee (D-Oakland), as well as Republicans Eric Early, a Los Angeles attorney, and former Dodgers and Padres first baseman Steve Garvey.

Seeing two Senate races on each ballot could tempt voters to split their vote, rather than backing the same candidate twice, said Paul Mitchell, a veteran Democratic strategist and pollster. The risk of a “head” vote and a “heart” vote, he said, is something the campaigns need to worry about.

For example, a liberal baseball fan could cast a nostalgic vote supporting Garvey, a former Dodgers All-Star, for the short-term special election, and a Democrat for the full six-year term. Admirers of Lee, who is lagging in fundraising and in opinion polls, could choose the veteran Oakland lawmaker to finish the rest of Feinstein’s term but back another candidate to take the job full time starting in 2025.

The two Senate elections in 2024 also poses a rare opportunity for candidates to double the amount of money that they are legally allowed to raise from each donor.

Federal campaign rules prohibit donors from contributing more than $3,300 to a candidate in a primary election and $3,300 to a candidate in the general election. With a second election on the ballot, the maximum allowable donation will rise from $6,600 to $13,200.

A spokesman for the California Secretary of State confirmed that both races will appear on the March and November ballots, but would not identify the candidates who have already filed to run in both. Spokesman Joe Kocurek said candidates have until Dec. 8 to file to run in the Senate race and state elections officials don’t certify the list of qualified candidates until Dec. 28.

Democratic activist and labor leader Laphonza Butler was appointed by Gov. Gavin Newsom to fill Feinstein’s seat after her death earlier this year.

Butler said last month that she would not seek a full term. Butler has not said whether she will run to serve out Feinstein’s term, which ends in January 2025, but someone familiar with her plans who was not authorized to speak publicly about them said she is not.

So Butler will serve through November 2024, the candidate that wins the special election will then serve until early January 2025, when the winner of the full six-year term takes office.

Early and representatives for Schiff, Lee, Porter and Garvey confirmed they had filed for both races.

Darry Sragow, the publisher of the nonpartisan California Target Book, which tracks statewide and legislative contests, said the multiple contests on the ballot are a disservice to the California electorate.

“From my point of view, the way this is constructed with the simultaneous or parallel elections has got to be confusing to a lot of voters,” he said. “Irrespective of who comes out of this as a winner, that’s not a good thing.”

But, the veteran Democratic strategist said, it also creates “fascinating possibilities.”

“All you can say is that the outcome is totally unclear,” Sragow said.

The 2024 election will mark the second time in two years that Californians have voted four times in the same year on a U.S. Senate seat. In 2022, voters saw Sen. Alex Padilla on the ballot four times, after then Sen.-Kamala Harris was sworn in as vice president and Newsom appointed Padilla to replace her in the Senate.

California has historically allowed appointed Senators to serve for the remainder of the term without an election if the term ends in January following the next regularly scheduled statewide election. But federal court rulings in Arizona and Illinois suggested that the Golden State’s longstanding practice of filling Senate vacancies could be illegal under the 17th Amendment to the U.S. Constitution, which mandated that senators be elected by voters in each state.

In 2021, after Padilla was appointed, Newsom signed a bill into law that requires a primary and general election to fill vacant Senate seats. Padilla filed to run for the remainder of Harris’s term and the subsequent full six-year term, winning both elections by a wide margin.

Democratic strategist David Beltran, who was a consultant on Padilla’s 2022 campaign, said they addressed the parallel elections on the ballot by hammering home a simple message in fliers, speeches and other campaign communications.

“It was about repetition,” Beltran said. “Just reminding people: Vote twice.”

The 2024 campaign is far more competitive than 2022. Some of the candidates vying to replace Feinstein have been campaigning for nearly a year. The candidates have reported raising more than $52 million thus far.

It’s possible that in such a competitive field, split-ticket votes could actually make a difference, experts said.

“In a crowded field of contenders, each with their own appeal, being on both ballots could potentially pose some risk,” Mitchell wrote of the 2024 election. “Even a small splitting of votes because of this ballot oddity could cause a candidate to make the runoff in the special election for the remainder term, and not make the runoff in the election for the full term.”

Mitchell’s interest in parallel elections was piqued in 2018. After state Sen. Tony Mendoza resigned amid allegations of sexual harassment, Montebello Mayor Vanessa Delgado and Pico Rivera City Councilman Bob Archuleta ran to fill the remainder of his term and to represent the 32nd District in a new four-year term. All three are Democrats.

Delgado was elected to complete the final 112 days of Mendoza’s term, while Archuleta won the full four-year term. The result suggested that a “shockingly large” number of district residents switched their votes, Mitchell said.

“Everyone was like, ‘How did that happen? That makes no sense,’” Mitchell said, noting that people went to the county Registrar of Voters’ Office to examine ballots to see if they were were flawed, in search of some reason to explain the split outcome.

“I think people got a little confused,” he said.