Congressman Adam Schiff appears to have the wind at his back in the blockbuster 2024 California Senate race as candidates on the Democratic side prepare for what is likely to be the most expensive Senate primary of all time.

The race in California is to replace Senator Feinstein, 89, who is retiring due to health issues that have already kept her out of the Senate for months in 2023.

The seat, almost guaranteed to go Democratic, has attracted some of the most high-profile names in the Democratic House conference and is expected to pit factions in the party against one another as candidates pursue a top-two spot in California’s nonpartisan primary.

Mr. Schiff appears to have gained an early financial advantage, breaking the fundraising record for the second quarter of a non-election year and hauling in $8.1 million, according to an early report in Politico.

Mr. Schiff, best known for his role in the impeachments of President Trump, brought in the money as the House GOP moved to censure him for his criticism of Mr. Trump.

During the censure proceedings, Mr. Schiff seemed to relish antagonizing his Republican colleagues in the House. “You honor me with your enmity,” Mr. Schiff said of his GOP critics ahead of the final vote. “You flatter me with this falsehood.”

While the official fundraising reports for the second quarter will be disclosed by the Federal Election Commission later this month, the fundraising haul probably makes Mr. Schiff the best-funded candidate in the California race.

The latest election finance data shows Mr. Schiff has $24.6 million on hand for his Senate campaign, whereas his main primary opponents, Congresswomen Katie Porter and Barbara Lee, have $6 million and $1.2 million, respectively.

Considering that a Democrat will almost certainly win the general election, an associate editor at Sabato’s Crystal Ball at the University of Virginia Center for Politics, Miles Coleman, says the race could become a “money fit” for Democrats.

“It may be a bit counterintuitive, but it’s easy to see why national Democrats would prefer a Democrat versus Republican general election,” Mr. Coleman told the Sun. “A race between Schiff and Porter, two strong fundraisers — or even Schiff against Lee — would attract untold millions from donors who may otherwise consider giving to Democrats in more marginal states.”

Given the massive fundraising lead and support from some of the biggest names in California politics, like Speaker Pelosi, it’s easy to see Mr. Schiff as an early favorite in the race.

Yet what polling has been done on the primary in California suggests that it’s still anyone’s game. A June Emerson College and Inside California Politics poll found that Mr. Schiff enjoyed 14.5 percent support, versus Ms. Porter’s 14.2 percent, in the primary.

Ms. Lee was third with 6.2 percent support. The highest-polling Republican candidates were veteran James Bradley, at 4.3 percent, and attorney Eric Early, who had 2.8 percent support.

Compared to the Democratic candidates, the Republicans have raised almost no money, with Mr. Bradley’s campaign having $73 on hand and Mr. Early reporting no fundraising at all.

Mr. Coleman says that, considering that there was no Republicans on the Senate ballot in 2016 and 2018 in California, and the heavy fundraising on the Democratic side, even a well-known GOP candidate could have a hard time getting on the general election ballot.

“My guess is that unless a big-name Republican gets into the race — perhaps someone from the House delegation or a prominent legislator — the general election will be two Democrats,” Mr. Coleman said.

Given California’s top-two primary system, it’s possible that none of the Republicans will even make it on the general election ballot. After votes are tallied in the state’s single nonpartisan primary, only the top two vote-getters will advance to the general election.

In the 2022 Senate election, Senator Padilla carried 61 percent of the vote compared to the 39 percent support that the Republican candidate, Mark Meuser, received.

In the primary, low Republican turnout meant that the GOP candidate with the most votes, Mr. Meuser, received less than half of the total of Mr. Padilla, at 1 million versus 3.7 million votes.

In a scenario with similar turnout, the top two Democrats could both carry more votes than any Republican in the primary, which would make the general election a faceoff between two of the top three candidates on the Democratic side, Mr. Schiff, Ms. Porter, and Ms. Lee.

This means that all the money these candidates are raising is likely going to be spent campaigning against other Democrats, and factions are already forming.

While Mr. Schiff has the support of Speaker Pelosi, Ms. Lee has garnered the support of the likes of Congressman Ro Khanna and the Los Angeles mayor, Karen Bass. 

Governor Newsom’s promise to appoint a Black woman to Ms. Feinstein’s seat, should the need arise, also suggests that Ms. Lee could be a top choice for the appointment if Ms. Feinstein is unable to finish her term. Ms. Lee is currently the highest-ranking black woman in Democratic congressional leadership.

An appointment could give Ms. Lee a big boost in the election. Mr. Padilla, for instance, benefited in 2022 from running as an incumbent after being appointed to fill Vice President Harris’s Senate seat.

Despite her lack of high-profile endorsements, Ms. Porter has consistently posted competitive polling numbers with Mr. Schiff and has garnered support from the liberal wing of the Democratic Party, though the liberal wing is currently split between Ms. Lee and Ms. Porter.