LOS ANGELES — California’s Senate race was expected to be a three-way Democratic prizefight, but the possibility of a record-low turnout is elevating the chances of Republican Steve Garvey, a former baseball star, and could derail the congressional careers of two prominent progressives.

In a year headlined by a likely presidential rematch that many Americans are dreading, California voters thus far have been sluggish to return mail-in ballots that were sent to 22 million homes earlier this month. The relative trickle of ballots has tended to come from older, white, conservative-leaning homeowners, a sweet spot for Republicans such as Garvey, a one-time National League MVP who played for the Los Angeles Dodgers and the San Diego Padres.

For months, Rep. Adam Schiff has had the fundraising and polling edge in a crowded Democratic field. Garvey’s ascent has imperiled the political prospects of Reps. Barbara Lee and Katie Porter. The top two finishers in the March 5 contest, regardless of party, advance to the general election in November in the liberal-leaning state.

“We’re at a real risk of losing,” Porter’s campaign warned in fundraising emails. Without more financial support, the plea went, “Katie is out of Congress for good.”

Schiff was a leading voice in the two impeachments of former President Donald Trump. Lee is a former chair of the Congressional Black Caucus. Porter has drawn attention on social media with her sharp questioning of tech CEOs in Capitol Hill hearings.

After the death of Democratic Sen. Dianne Feinstein in September, all three entered the race. Porter is leaving her swing district in Southern California as Democrats try to regain control of the House, where Republicans now hold a slim edge.

Presidential elections usually drive Democratic turnout in California, but that hasn’t been the case this year, with President Joe Biden and Republican Donald Trump on track for a second matchup in which both are viewed unfavorably by many voters.

“This is a low-interest, low-turnout kind of election cycle. That generally creates an electorate that is older, more conservative, whiter,” said Paul Mitchell of Political Data Inc., a research firm that closely tracks voting trends and works with Democrats, independent candidates and academics.

While the dynamic could shift by the time primary voting ends, Mitchell said it’s possible that Garvey ends up with the highest total as the Democratic candidates splinter votes on the left.

“I don’t see a surge of Democratic turnout coming in the end, but there could be a surge of Republican voters in the end,” Mitchell said. He said that could be driven by those voters influenced by Trump’s unsupported claims of election fraud who will vote in-person rather than through the mail.

Schiff told reporters recently that he was concerned “for the sake of our democracy” about a low turnout. His campaign has sent 3 million texts and made over 50,000 phone calls to potential supporters so far.

Last spring, the race looked like it would revolve around Schiff, Porter and Lee, who are largely indistinguishable on policy but bring different backgrounds and styles to the contest. Garvey, after years of flirting with politics, entered the race in October and gave Republicans a recognizable name on the ballot. He retired from baseball nearly four decades ago, in 1987, and had to overcome the resurfacing of tawdry details about his private life, including having two children with women he wasn’t married to, that had undercut the clean-cut public persona he cultivated in his Dodger days.

A Republican hasn’t won a Senate race in California since 1988, and registered Democrats hold a 2-to-1 advantage over Republicans statewide.

In all, more than two dozen names will appear on the Senate ballot for the six-year term that begins next year. Many of those candidates are political unknowns.

The race was once anticipated as a showcase of Democratic rivalries on the party’s left wing. That never materialized.

Schiff emerged as the establishment pick with endorsements from former House Speaker Nancy Pelosi, most of California’s congressional delegation and former Democratic Sen. Barbara Boxer. His fundraising prowess — he had $35 million on hand at the end of the year — has allowed him to roll out a steady stream of TV and digital ads, backed by a barrage from supportive super political action committees.

According to data from media tracking firm AdImpact, Schiff’s campaign has had almost a 2-to-1 advertising advantage over his nearest rival, spending $28.2 million through Wednesday, followed by Porter at $14.6 million. Lee had $1.3 million in buys.

Porter’s campaign has accused Schiff and his supporters of running ads intentionally spotlighting Garvey to lift the former baseball star’s profile with Republicans, on the premise that having a GOP opponent would presumably be an easier match for Schiff in the fall.

“Garvey himself hasn’t run a single TV ad, but his name and face are all over California’s TVs thanks to this cynical play,” Porter’s campaign said in an email.

Porter, who presents herself as a suburban soccer mom out to protect the middle class, has warned that ”billionaires, establishment politicians and corporate special interests are trying to buy this race, and it looks like their plan might work.”

Schiff defends his ads and told reporters that Garvey has attacked him in debates and interviews. “I’m not going to ignore him.”

Lee, a longtime standard-bearer in the party’s progressive wing, has struggled to raise money. The lack of cash has left Lee, who has proposed a $50-an-hour federal minimum wage and was the only member of Congress to vote against authorizing military force after the Sept. 11 terrorist attacks, lagging in polling.

Democratic pollster Ben Tulchin calls Lee and Porter “iconic liberal stars,” but says Schiff’s financial advantage appears decisive.

Porter spent nearly $29 million to defend her district in coastal Orange County in 2022, while Schiff was running in a safe Democratic district.

“You have three talented, impressive Democrats running,” Tulchin said, “but only one can win.”