But California Republicans are such a distinct minority group in the blue state — they make up about a third of the electorate — that, this go around, things could get weird. The race to replace Feinstein could end up as a Democrat-on-Democrat contest, and Republicans could wind up swinging the whole election. It’s also not clear who might benefit.

Porter’s campaign seems obsessed with this idea. My POLITICO colleague Chris Cadelago reports that such a scenario is “a frequent line of questioning” in meetings between Porter’s campaign staff and Democratic activists.

Here are necessary conditions for that to happen, and what it would mean for the general election next November:

The polling in this race comes with a huge caveat

According to the University of California, Berkeley’s Institute of Governmental Studies latest poll, out this week, the race could end up actually with a Republican in the final two.

Eric Early, a perennial GOP candidate who is running for Senate, has the support of 18 percent of registered voters. Porter is at 17 percent, Schiff at 14 percent and Lee at 9 percent. The leading Democrat only needs a plurality of 60 percent of the Democratic-leaning vote in California to be the likely winner in November — if that GOP number is real.

“With three [Democrats], that’s when I think you have a greater possibility that the Republican can emerge as one of the top two finishers,” said Mark DiCamillo, who conducted the poll.

And, there’s reason to think Republican candidate Early could get a boost. Since the primary is being held on 2024’s Super Tuesday, the presidential primary will likely be a big draw, and all of the action is in the GOP race.

But the path to two Democrats isn’t impossible

A few factors this year could lead to a Democratic faceoff.

First, Early’s numbers could be inflated. He was the only Republican candidate listed in the survey, but he’s likely to face others. Last year’s Senate primary featured 10 candidates who identified as Republicans — the second-place finisher, Mark Meuser, earned just 15 percent of the vote.

And while the three Democratic members of Congress are often grouped together, the polling and fundraising data suggest that Porter and Schiff are currently in a different tier than Lee. Even Lee’s internal primary polling only has her at 11 percent. The only Black candidate in the race is also well behind Porter and Schiff in fundraising. At the end of March, Lee had $1.2 million in cash on hand, well less than Porter ($9.5 million) and Schiff ($24.7 million).

“The open question is how competitive Lee would get,” said DiCamillo, the UC-Berkeley pollster. “If she’s going to have enough funding to get her message across, she certainly has a story to tell. If she still lags, that actually increases the odds of the top two Democrats — Porter and Schiff — moving forward.”

California Gov. Gavin Newsom has promised to appoint a Black woman if Feinstein should retire or pass away before her term is up. If he holds that promise, and chooses Lee as a replacement, it could potentially give her a big boost.

In a race between two Democrats, Republicans could decide

None of the Democrats running for Feinstein’s seat has an obvious path to either consolidating the state’s Democrats or creating cross-party appeal to attract Republicans.

Of the three Democratic candidates, Schiff’s voting record is the least liberal. On paper, that would potentially be more attractive to Republican voters, who would be without a candidate of their own in this scenario. But Schiff is perhaps best known for his role in investigating and impeaching then-President Donald Trump — something likely to actively repel the state’s Republicans.

He’s such a villain in GOP circles that House Speaker Kevin McCarthy made it a point of kicking him off the Intelligence Committee, and one first-term GOP member has even floated expelling Schiff from the chamber entirely in a tit-for-tat over the fate of Rep. George Santos (R-N.Y.), an accused felon.

There’s always the possibility of Republicans issuing a protest vote. In 2018, Kevin de León, a former state Senate leader who’s now serving on the Los Angeles City Council, attracted a number of Republican votes, even though he was challenging Feinstein from the left.

Feinstein’s biggest margins were in the heavily Democratic counties of Los Angeles (58 percent), San Francisco (63 percent) and Marin (65 percent) — even though the statewide outcome was 54-46. De León’s best numbers came from Trump country.

It’s not clear whether the more liberal Lee or Porter would benefit from Republicans disliking Schiff. A large chunk of them could leave the race blank. In 2018, 12.5 million votes were cast in the governor’s race, which featured Newsom against Republican Dan Cox. But only 11.1 million were cast in the Feinstein-de León race, which was on the same ballot.

While there are a lot of unknowable variables in his race, one thing does seem relatively certain: It’s unlikely a Republican candidate will win. Republicans haven’t won a statewide election in California since 2006, and the best showing for a Republican presidential candidate in recent years was when former President George W. Bush broke the 40 percent mark in 2004.