Rep. Katie Porter, famed among Democrats for grilling powerful corporate barons and right-wing ideologues testifying before Congress, faces a serious risk of falling short in Tuesday’s California primary election, which would bring an end to her bid to win the late Dianne Feinstein’s Senate seat in the fall general election.

Along with a once-formidable campaign account depleted by her tough 2022 reelection bid and expected low voter turnout, the Irvine congresswoman must overcome the millions of dollars Democratic rival Rep. Adam B. Schiff of Burbank and his allies have spent boosting GOP candidate Steve Garvey, the former Dodgers All-Star first baseman.

If Garvey and Schiff win the top two spots in California’s open primary, the two would be the only candidates to advance to the November general election — with Schiff being the heavy favorite because of California’s strong Democratic tilt. Political experts say Schiff’s strategy to prop up Garvey is largely driven by the threat he would face in a one-on-one face-off against Porter in the fall election.

“She would give him a hell of a run in the general election — he would look like the establishment Washington, D.C., insider, and she could have contrasted herself with him,” said GOP strategist Kevin Spillane, who is undecided in the race. “That’s pretty remarkable. Schiff’s working harder to get Garvey in the runoff than Garvey is himself.”

Spillane said he could not recall anyone spending as much to buoy a statewide GOP candidate since then-Republican gubernatorial candidate Meg Whitman in 2010. Ad campaigns portray Garvey as a loyalist of former President Trump and the biggest political threat to Schiff, an effort largely expected to increase Garvey’s appeal among Republican voters.

The strategy is partly driven by California’s top-two primary system approved by voters more than a decade ago, which allows only the two candidates who secure the most votes to advance to the general election, regardless of their political party affiliation.

But this year’s Senate contest — a rare open seat for a Californian in the nation’s top legislative body — is also shaped by the records and personalities of the top Democrats in the race.

Schiff and Porter are both liberal Democrats, prodigious fundraisers and well-known voices among cable news show viewers across the nation, but a contest between them in the general election would be much different from their current primary battle.

Schiff, who was elected to Congress as a moderate in 2000, has won over most of the Democratic establishment’s leadership, starting with former House Speaker Nancy Pelosi (D-San Francisco). He is now best known by many voters as the manager of Congress’ first impeachment trial of Trump over foreign interference in the 2020 election and his vocal role in the 2021 House investigation into Trump’s accountability for the Jan. 6 insurrection at the U.S. Capitol.

Although Porter’s voting record is practically identical to Schiff’s, she has honed a populist patina, blasting corporate leaders during congressional oversight hearings and focusing on issues such as income inequality. The former UC Irvine law professor’s background as a minivan-driving single mother also appeals to moderate voters in her sharply divided suburban Orange County congressional district.

“Part of her persona is that she’s authentic. I think she is trying to connect with normal voters who face the same kitchen table issues she does and talks about as a single mom,” said Thad Kousser, a political science professor at UC San Diego. “That’s part of her appeal and could lead to her getting moderate support in the general.”

Porter’s positioning — combined with Schiff being among the most prominent anti-Trump faces in the nation — could boost her in a general election contest because she could win anti-Schiff Republican voters, he added.

“I don’t think she has built up a wall against her with Republicans as he has because he’s been such a prominent figure as a leader of the impeachment. That’s helped him [in the primary], but that’s a double-edged sword” in the general election, Kousser said.

But Porter’s prospects of reaching the November ballot are, at best, uncertain. A new poll finds her in third place in the primary, and early ballot returns show a sluggish turnout among the voters most likely to support her, compared with Schiff and Garvey.

Garvey and Schiff are in a statistical tie for the top two spots, according to a poll released Thursday by UC Berkeley’s Institute of Governmental Studies and The Times.

Among likely primary voters, Garvey received the backing of 27%, while Schiff won 25%, within the poll’s margin of error. Porter received the support of 19%, and fellow Democratic Rep. Barbara Lee of Oakland got 8%. Slightly more than 1 in 10 supported other candidates, while 9% said they were undecided.

The mail-in ballots that already have been cast favor Garvey over Porter.

Though there are far more Democratic registered voters in the state than Republicans, GOP voters have cast a greater share of their ballots, 15% compared with 13% of Democrats through Friday, according to a ballot tracker run by PDI, a political data firm that caters to Democratic and nonpartisan candidates.

Paul Mitchell, a veteran Democratic strategist who is the vice president of PDI, expects low voter turnout in the election, reflecting a lack of enthusiasm driven by the reality that President Biden and Trump have all but secured their parties’ nominations for president.

“It’s just an uninteresting national ballot,” he said.

Low turnout would help Garvey, since Republicans appear to have a greater propensity to cast ballots in the primary. Plus, if, as multiple polls suggest, GOP voters have consolidated behind Garvey while Democrats are split among multiple candidates, that alone could be enough to help Garvey win one of the top two spots on Tuesday.

Additionally, young people and voters of color — who are more likely to support Porter in the Senate race — are voting with much lower frequency than older, white voters, according to the data.

One caveat is that Tuesday is the first presidential primary California has conducted since it began mailing ballots to every registered voter during the pandemic.

“It’s still too early to tell about turnout, but obviously it’s not trending very high. But every voter gets a ballot sent to them these days,” noted Democratic pollster Ben Tulchin, who is not involved with any candidates in the race. “I expect turnout to be lower for sure but it’s still too early to say how low it’s going to be. Porter seems to be in a tough spot, but I think there is still a chance she can make it through.”

But he added that Porter’s challenges are compounded by how greatly Schiff has outspent her in this race and how much she had to spend in her tight 2022 congressional reelection campaign.

While both of them were among the most prodigious fundraisers in Congress, Schiff entered the race with far more money and has raised more than Porter has since.

More than $65 million has been spent in the race, making it the most expensive Senate contest in California history, according to data firm AdImpact. The firm tweeted Friday morning that 60% of Schiff’s broadcast ads mention Garvey.

Most of these funds have been spent by Schiff and his allies, including independent expenditure committees funded by Native American tribes and cryptocurrency billionaires, not only supporting his Senate bid and attacking Porter but also boosting Garvey’s profile among Republicans.

Broadcast and cable stations have been blanketed by ads about the race, including a Schiff message about Garvey airing on Fox News, despite the candidate calling for a boycott of advertising on the cable station because of its false reporting about the 2020 election.

Speaking on MSNBC in 2023 after entering the Senate contest, Schiff referred to “folks that continue to advertise on stations that deliberately put out lies and deliberately undermine our elections. They become culpable in this too.”

In the last week, Schiff’s campaign spent $390,152 highlighting Garvey’s candidacy on Fox News, according to Democratic media buyer Sheri Sadler, who is not working for any candidate in the race.

The Schiff campaign declined to comment about the candidate’s efforts to boost Garvey.

A Garvey spokesman said the Republican’s improved standing in the polls was the result of Californians becoming “reacquainted” with the retired ballplayer and learning about his priorities.

“With Adam Schiff’s aggressive campaign against Garvey and the latest primary poll results, our predictions are proving accurate,” spokesman Matt Shupe said. “Garvey’s half-century bond with Californians transcend politics, and will prove to be a formidable force in both the primary and general elections.”

The Porter campaign did not respond to a request for comment, but the candidate has repeatedly fundraised off the Schiff campaign’s focus on Garvey.

“If I advance to the general election, there’s a good chance we will win that race,” Porter wrote in one of four email blasts to supporters Thursday. “That’s why super PACs and the Schiff campaign are doing everything they can to prevent me from advancing, and I won’t BS you: their plan might work.”