Dianne Feinstein, 89, the longest-serving woman in the Senate, is still not back in Washington after being hospitalized with shingles earlier this year. Her absence is holding up crucial judicial confirmations for the Biden administration, and has reignited questions about her mental acuity and ability to serve, as well as calls from prominent members of her own party to step down.

Feinstein’s future has refocused attention on an already huge 2024 election in Democratic politics — the race for her California Senate seat. Since Feinstein has announced that she will not seek reelection, the contest to replace her pits three of the Democratic Party’s most recognizable and influential lawmakers against each other in a standoff that could be one of the most expensive Senate races in history. Whoever that ends up being will be a stark contrast to Feinstein. And a California Senate seat is something like a beacon for Democratic politics, a signal of the will and identity of the country’s largest blue bastion.

The longstanding questions about Feinstein came to a head this month, after a series of stories questioned if she was still fit to serve. In February, she bowed to some pressure, saying she would retire at the end of her term, but the calls for her to step down early have only intensified since she left DC in early March.

Though Feinstein’s future remains in question, the fight to succeed her has been taking shape in the background for months. That star-studded (at least as far as politics goes) contest for Feinstein’s seat kicked off in January when Rep. Katie Porter, the darling of the modern progressive wing in Congress, announced her candidacy as California was enduring historic storms and flooding. Anti-Trump #Resistance hero Rep. Adam Schiff, who started his career as a moderate, followed with an announcement shortly thereafter, and a third candidate, Rep. Barbara Lee, a pioneering Black activist and the most liberal member of Congress, officially jumped into the contest in February.

Whoever wins this contest could hold the seat for as long as they want — California rarely has Senate vacancies. And California voters may stand ready to make a few pronouncements about just how progressive they want their lawmakers to be and the kind of track record they want to reward.

How does California elect senators?

The first thing to understand about this primary contest is that California has a unique way of running its state elections. It runs an open primary — meaning voters can select candidates from any party, not just their own — in which the two candidates who receive the most votes move on to the ballot for the general election. The primary election is held in March, and we’re a little under a year away from the first votes being cast.

That top-two system, and the California GOP’s slide into irrelevance, has generally meant that Republicans are shut out of general elections in California. That’s happened during the last two competitive Senate elections in the state, which were both between Democrats: in 2016, when Kamala Harris beat Loretta Sanchez, and in 2018, when Feinstein beat state Sen. Kevin de Leon.

In both of those elections, voters seemed to have obvious choices: Harris was the state’s attorney general, and generally benefited from greater name recognition than Sanchez, an obscure congresswoman from Southern California. And in 2018, Feinstein was the incumbent senator, benefiting from decades of statewide campaigning.

This time around, neither Porter, Schiff, or Lee immediately stands out as a far-and-away frontrunner. They all belong to the same left flank of the national Democratic Party, but not all of them can claim the same level of ideological purity.

Who is Adam Schiff?

At this point in the race, Schiff has the broadest support from the institutional Democratic Party. He’s been endorsed by the vast majority of California’s congressional delegation, including former Speaker Nancy Pelosi, and scores of local and state elected officials. All that makes sense: He’s served in Congress for 12 terms, representing his Los Angeles County-based seat since 2001, and served in the state senate before that for one term starting in 1996.

He leaned into his legal and foreign policy expertise during his time in Congress, serving on the House Foreign Affairs Committee, the Benghazi Select Committee, and as chair of the House Intelligence Committee during the Trump years. But it was the Trump years that made him a national star: He was the Democrats’ main Trump antagonist during the Russia investigations, the Ukraine impeachment inquiry and Senate trial, and the January 6 hearings, regularly appearing on cable news.

But Schiff’s time in Congress has also been an ideological evolution. He was first elected as a moderate in a district that had been held by Republicans but was drifting toward Democrats; he’s been a member of the centrist and bipartisan-minded Blue Dog and New Democrat coalitions, and supported standard moderate ideas, like balancing the budget, increasing defense spending, and supporting the business community in California.

Schiff now claims the progressive mantle — and though colleagues to his ideological left have rebuffed his efforts to join them in the Congressional Progressive Caucus, he has moved to the left as his party has shifted as well. He is more critical of the executive branch’s war powers claims, has advocated for a constitutional amendment to overturn the Citizens United Supreme Court decision, and now endorses Medicare-for-all.

Who is Barbara Lee?

Schiff’s time in Congress also sets up a key contrast with his colleague Barbara Lee.

Both served in Congress in the aftermath of 9/11, but while Lee voted against the authorization for the use of military force that gave former President George W. Bush a blank check on anti-terrorism war powers, Schiff voted for it.

Lee took a tremendous amount of criticism for being the lone “no” vote during that tense time in American politics — but that independence has been a calling card for her during her 25 years in Congress, and especially in her early career. She was elected in 1998 during a special election to succeed her former boss, Rep. Ron Dellums, who was a notable socialist candidate, critic of the Nixon presidency, and anti-apartheid activist.

Though Lee, like Schiff and Porter, wasn’t born in California, she got her start in politics in the Bay Area, while attending Mills College in Oakland. There, she invited the trailblazing Black politician Shirley Chisholm to speak on campus, eventually joined Chisholm’s 1972 presidential campaign, and served as a delegate during that year’s Democratic National Convention. Lee was also involved with the local chapter of the Black Panther Party, and worked for Black Panther co-founder Bobby Seale’s mayoral campaign.

So far, Lee has relied on this early legacy, and her track record in Congress, to distinguish herself from her rivals. She has long been considered one of the most liberal members of Congress, and has led the Congressional Progressive Caucus, the Congressional Black Caucus, and the Congressional Cannabis Caucus, and co-founded the LGBTQ+ Equality Caucus.

Who is Katie Porter?

For those in the left-wing spaces who know, Lee is a progressive legend. But she risks being locked out of the general election by a younger, newer face of Democratic progressivism: Katie Porter.

Porter is the newest legislator of the bunch, elected to represent a swing district in Orange County (south of Los Angeles) during the 2018 blue wave, and is one of the best-known members of Congress. Her legal and academic background made her a star during House hearings and she’s generated viral moments with her whiteboard (she, like her mentor Sen. Elizabeth Warren, is a former college professor) and her trolling of Republicans during the House leadership elections. Those moments have been amplified through her social media channels, including her official and campaign TikTok accounts, which have more than 400,000 followers combined — significant for a politician, and among the most-followed members of Congress on the app.

Porter was the first to kick off her campaign, and in doing so was the first Senate hopeful to essentially pressure Feinstein into retiring. That Porter would enter the race was expected. Her shadow campaign effort to consolidate support behind her Senate bid was widely covered last year, and she has been one of the party’s best fundraisers for years now. She entered the race with the backing of plenty of progressive politicians and political groups, and was the first to put out polling showing her strength in an open primary, and in head-to-head matchups with Schiff.

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Porter and Lee also represent a kind of ideological purity that Schiff cannot claim: Both have served in leadership of the Congressional Progressive Caucus, while Schiff recently had to withdraw his request to join the CPC, which NBC News reported as being partially because “the group wasn’t going to let him in.” Whether that “progressive” label matters, however, might be borne out during this election.

Race, gender, and geography will shape the California Senate race

There are three main factors that California political experts tell me will determine this outcome: the race, gender, and geography of the electorate and the candidates.

At the moment, Alex Padilla, California’s other senator, stands as the state’s first Latino senator, and the first senator from Southern California in three decades. Would California voters want to go from having two trailblazing women senators to two male senators in the span of four years? Would they choose a white progressive over a Black woman when the Senate lacks any Black female representation (a pitch Lee and her campaign are making)? Or would California voters select another senator from the southern half of the state, when Northern California has traditionally tended to dominate the state’s politics?

California’s 27 million eligible voters are not the same as the state’s likely electorate, which is more white than the overall voting population. Likely voters are overwhelmingly Democratic (39 percent identify as liberals versus the roughly even 30 percent who call themselves moderates and conservatives), and are majority white, despite only making up about 40 percent of the state’s voting-age population, according to the Public Policy Institute of California. Latinos, who make up more than a third of adult Californians, only make up around 22 percent of likely voters, while Asian Americans are 13 percent of likely voters, and Black likely voters only make up about 5 percent.

Likely voters are also concentrated in the Bay Area, where the population tends to be whiter, wealthier, and better educated than in Southern California. The media market there is better consolidated than in other parts of the state, so money goes further on TV spending. As the only major candidate of color in the race, these dynamics pose both challenges and possibilities for Lee. Black voters are declining as a share of eligible voters in California, Mike Madrid, a longtime Republican political consultant, said, so Lee will have to rely on a lot more white voters. Madrid added that Lee will have to make inroads among Southern California Latino voters.

“Barbara Lee has regional strength, has strong progressive bona fides, and that she’s a Black woman all help,” Madrid said. “[A majority] of Democratic primary voters are women — despite conventional wisdom, being a woman is an advantage in the Democratic primary.”

For the last 30 years, at least one Senate seat has been held by a woman, giving Porter and Lee an additional case to make to voters to look beyond Schiff. “For Democratic voters, that’s going to be a factor in who they vote for,” Garry South, the Democratic strategist behind the successful California gubernatorial campaigns of Gray Davis, said. “Of course, not all women just vote for women, but among a certain slice of the electorate it’s going to weigh on their decision to not want to go from having two women representing us to two males.”

And, both race and gender merge into perhaps the biggest factor of all — the geography of each candidate’s political base. “A candidate from the Bay Area has an advantage over a candidate from the Southern California area because of the very high rates of turnout in the nine Bay Area counties,” South said.

That geographical split might not make its way into direct attacks between the candidates, however; the last time that kind of pitch was made was in 2016, when Loretta Sanchez complained to voters that Harris would be another politician from the Bay Area, which “controls everything.” That appeal flopped, and it didn’t help Sanchez’s floundering campaign.

South also noted another obstacle that geography poses for the three candidates: none of them have the kind of name identification that Feinstein, Harris, or former Sen. Barbara Boxer before them had. “It’s only been twice in 53 years that a sitting member of Congress has been elected to the US Senate in California. The last time was in 1992, and before that it was 1970. A sitting member of the state senate has a bigger constituency than a member of Congress does,” he said. “None of these three candidates are going to start out being very well known statewide.”

But that awareness will grow as the campaign unfolds — and money may be able to boost Porter and Schiff’s brand names into the north of the state enough to even out Lee’s recognition.

What California Senate race polls show

At this point in the race, we don’t have a lot of great data, but what we do have paints a picture of a race dominated by Porter and Schiff. As early as February, polling from UC Berkeley showed that Schiff and Porter each dominated around 20 percent of the electorate, with 8 percent backing Lee, 10 percent backing some other candidate, and nearly 40 percent of the electorate undecided.

Those undecided voters show the room each of these candidates have to make gains. When asked, large proportions of Democratic and independent voters told the Berkeley pollsters that they simply don’t have an opinion of the candidates because they don’t know about them. “Since so many voters are unfamiliar with the candidates, there is much potential for movement. It will likely be several months before most voters tune into the race, and a key challenge for each candidate will be to build a statewide following,” one of the directors of the Berkeley Institute of Governmental Studies said.

That poll also showed a generational divide in support for the candidates: older voters tend to favor Schiff, while younger voters, from 18 to 49, tend to back Porter by larger margins the younger they get.

And geographically, Porter has leads in her base of Orange County and in the Inland Empire (which borders Nevada and Arizona), and is running even with Schiff in Los Angeles County. Schiff, meanwhile, has modest leads in the Bay Area and along the Central Coast. These numbers mostly match the results of Porter’s internal polling — and her boosters are quick to point out that Schiff’s name recognition may end up being a liability among Republicans who decide to vote in the general election.

The picture looks the same when you look at fundraising. Before he launched his Senate campaign in late January, Schiff had the biggest war chest, with about $20 million in the bank compared to Porter’s $7 million and Lee’s $50,000 at the end of last year. By the end of the first quarter of 2023, Schiff and Porter reported huge numbers: Schiff had raised $6.5 million, for a total of $24.6 million of cash on hand, while Porter had raised $4.5 million, leaving her with $9.4 million available. Lee raised $1 million, for a total of $1.15 million.

“If you include all the finances, it reinforces what most people have observed and assumed going in: Adam Schiff is clearly the frontrunner, but not a prohibitive one,” Dan Schnur, a professor at UC Berkeley’s Institute of Government Studies and another longtime California political adviser, said. “He’s got a tremendous fundraising base, mostly from his own career, but also from the support he’s gotten from the congressional delegation.”

(One thing Porter’s supporters will add to that: Schiff is accepting donations from lobbyists, while Porter is not.)

But the scramble for money doesn’t cleanly reflect who is winning: Statewide California races are among the most expensive elections you can run in, and plenty of campaigns have been run with the backing of hundreds of millions of dollars, like former eBay CEO Meg Whitman, who spent nearly $140 million of her own money in unsuccessfully trying to beat California legend Jerry Brown for the governor’s office in 2010. “The only thing bigger than a California Senate race is a presidential race,” Madrid said. “But the money raised is not that important, until you start getting up into the $100 million range.”

Money will determine how long the candidates can stay in the running, and the 2024 primary is still a year away. But each of the big three campaigns are likely to make it through to the primary election. One thing is also likely: Republicans don’t really have any viable statewide options to run, and with an election as competitive as this, it seems more likely that Democrats will be energized to turn out and lock out Republicans from the general election ballot.

Whatever happens, California’s primary race may attract a lot of donor money that could be more useful for Democrats to spend in close, competitive elections, like those happening next door in Arizona and Nevada — which will actually determine the future of Senate control.

But that doesn’t mean this primary election doesn’t matter. Californians will answer many questions with their dollars, polling responses, and eventual votes. But the biggest one is likely to be a statement about the kind of progressive state it really is.

“The main question is, in the bluest state, with the whitest, wealthiest, most progressive voters in America, do they genuinely prioritize racial and ethnic diversity?” Madrid said. “That’s the only question that will be answered. Barbara Lee is as progressive as anybody else, she’s a woman, she has more experience than the other two probably combined, she checks literally every box except for one: she is not white,” Madrid said.