AMNA NAWAZ: Well, one of the most watched non-presidential races of the day is in California.

GEOFF BENNETT: Voters there are deciding who should fill a U.S. Senate seat.

And, as Laura Barron-Lopez explains, today's primary will determine whether the race is just the beginning or essentially the end.

LAURA BARRON-LOPEZ: Super Tuesday's blockbuster drama will be in California, where 11 Democrats and 10 Republicans are competing for the state's open Senate seat.

Only the top two finishers, regardless of party, will remain in the race.

ERIKA CAMPOS, Democratic Voter: I am still doing my homework.

I'm not completely ready to decide who my next senator is going to be.

LAURA BARRON-LOPEZ: For Democrats, there are three leading contenders, all self-described progressives already serving in the House.

REP. ADAM SCHIFF (D-CA), Senatorial Candidate: This will set a new precedent.

LAURA BARRON-LOPEZ: Adam Schiff is best known for trying former President Trump's first impeachment trial.

REP. ADAM SCHIFF: I think Californians are looking for a senator who leads in the big fights.

When our democracy was at risk, when we had a man who would be a dictator as president, I was in the center of that fight, protecting our institutions.

REP. KATIE PORTER (D-CA), Senatorial Candidate: This all totals up to 1,000.

LAURA BARRON-LOPEZ: Katie Porter became a viral sensation with her pointed whiteboard interrogations in committee.

REP. KATIE PORTER: I went in really prepared, asking tough questions of people like bank CEOs about why their workers can't put food on the table, asking tough questions, and, more importantly, getting answers.

And I think that's a really important part of the Senate and the House that, frankly, we aren't seeing Democrats or Republicans do enough of.

REP. BARBARA LEE (D-CA), Senatorial Candidate: I rise today really with a very heavy heart.

LAURA BARRON-LOPEZ: Barbara Lee's national profile dates back to a vote she cast more than 22 years ago.

REP. BARBARA LEE: This unspeakable act on the United States has really forced me, however, to rely on my moral compass, my conscience, and my God.

LAURA BARRON-LOPEZ: The only lawmaker who opposed authorizing military force in the days immediately following 9/11.

REP. BARBARA LEE: I voted against that, and I said it could escalate out of control, and it did.

LAURA BARRON-LOPEZ: Democrats outnumber Republicans 2-1 here in California.

But with the party's vote split between three well-known candidates and low expected turnout, a Republican could make it through to November.

STEVE GARVEY (R), California Senatorial Candidate: We need to build consensus now more than ever.

It makes me think, hasn't anybody played a team sport in Congress?

LAURA BARRON-LOPEZ: Former L.A. Dodger and Republican front-runner Steve Garvey leans on sports metaphors while claiming moderate conservative principles.

But the first-time candidate offers few specifics or a concrete policy platform, saying he's just trying to listen right now.

KEITH CURRY, Former Newport Beach, California, Mayor: We're in a time where people are very angry with the issues.

They're angry about homelessness.

They're angry about crime.

They're angry about the economy.

And they're angry about the border.

And that creates an environment where an outsider with commonsense solutions like Steve Garvey can be heard and be an effective candidate.

LAURA BARRON-LOPEZ: Keith Curry, the former Republican mayor of Newport Beach, is backing Garvey.

KEITH CURRY: There's no doubt that it's difficult for a Republican running statewide in California.

LAURA BARRON-LOPEZ: Curry says star power can elevate California Republicans, like it did for Ronald Reagan and Arnold Schwarzenegger.

But Curry never supported Donald Trump.

And Garvey won't say who he's backing for president this year.

Steve Garvey voted for Trump twice.

Is that a problem for you at all?

KEITH CURRY: Most Republicans voted for Donald Trump.

And he's probably going to be the nominee this year.

He's not very popular in California, but he's going to be the nominee.

LAURA BARRON-LOPEZ: Garvey didn't respond to our request for an interview.

Over the weekend, Garvey surged in a new U.C.

Berkeley poll from a virtual tie for second place with Congresswoman Katie Porter to a statistical dead heat.

NARRATOR: Two leading candidates for Senate, two very different visions for California.

LAURA BARRON-LOPEZ: Garvey's rise follows massive ad buys from Schiff during the closing weeks, naming the Republican as his main competitor.

REP. ADAM SCHIFF: He's attacking me repeatedly on FOX.

And in a jungle primary, you can't ignore one of your leading opponents who's attacking you.

REP. KATIE PORTER: This is a huge choice for Californians.

LAURA BARRON-LOPEZ: Porter believes Schiff is boosting Garvey to guarantee a win for himself in November.

NARRATOR: Eric Early proudly stands with Donald Trump.

LAURA BARRON-LOPEZ: She's buying ads that say another Republican, Eric Early, is the true MAGA threat.

REP. KATIE PORTER: I don't think anyone should think that Steve Garvey is going to be California's next senator, but having him in this race all the way through November is a huge, huge gift to Republicans.

LAURA BARRON-LOPEZ: For most Democratic voters, the candidates differ more in personality than policy.

JOSEF LAYA, Democratic Voter: It will be hard for me to differentiate.

A lot of the times, it feels like I'm just tossing a coin in a bucket.

CATHRYN POSEY, Democratic Voter: Picking the right person feels really important, and it's pretty tough to narrow it down.

ARI BARUTH, Democratic Voter: Many of their policies are the same.

It's hard sometimes to tell where they overlap and where they don't overlap.

LAURA BARRON-LOPEZ: All three candidates support Medicare for all, have proposals to reduce the cost of housing, support abolishing the filibuster, and all three are worried about young voters' disillusionment with President Joe Biden and their party.

REP. BARBARA LEE: I want to make sure that young people know that their voices are being heard.

REP. KATIE PORTER: Right now in our U.S. Senate, we don't have nearly enough younger voices.

REP. ADAM SCHIFF: If I have a concern, it's about the youth vote.

LAURA BARRON-LOPEZ: In the final stretch, they're fighting to separate themselves from the pack.

REP. ADAM SCHIFF: I'm drawing the contrasts with my Democratic colleagues based on leadership and effectiveness.

LAURA BARRON-LOPEZ: Porter says she's immune to big money's influence, refusing to accept cash from corporations or lobbyists.

REP. KATIE PORTER: In my time in Congress, in my five years, I have done Congress differently.

LAURA BARRON-LOPEZ: Lee had to fight her high school's administration before earning a spot as the first Black woman on the cheerleading team.

And, unlike her opponents, she's experienced living unhoused.

REP. BARBARA LEE: We have families that can't afford childcare.

I know what that's like.

I have lived that.

LAURA BARRON-LOPEZ: If Democrats finish in first and second place, the race to November will be competitive.

LORI VELTRI, Republican Voter: I voted for Steve Garvey.

LAURA BARRON-LOPEZ: And why'd you vote for Garvey?

LORI VELTRI: Because I'm really tired of the Democratic policies.

LAURA BARRON-LOPEZ: But if voters pick a Democrat and a Republican, November will be almost certainly sewn up for the Democrat that makes it through.

For the "PBS NewsHour," I'm Laura Barron-Lopez.

AMNA NAWAZ: And we will have more live coverage of Super Tuesday online and later tonight beginning at 11:00 p.m. Eastern right here on PBS.