NEWPORT BEACH, California—Last month, at a politically themed chili cook-off in Huntington Beach, Sandy Metcalf’s manila folder went missing. The folder contained copies of documents alleging Hans Keirstead, a neuroscientist running for Congress in California’s 48th District, had slept with his graduate students and, in one case, had punched one of them in a boozy incident following a concert. Metcalf had left her purse unattended for “three to five minutes,” she told me, and when she next saw the folder, it was in the arms of Anita Narayana, the political director for Keirstead’s campaign.

To be fair, it’s not easy to keep track of all the sordid accusations and opposition research flying around in the 48th District, which covers much of the wealthy Orange County coast. For months now, Keirstead has been locked in a nasty battle with a fellow Democrat, real estate executive Harley Rouda, as they try to claw their way into second place in Tuesday’s “jungle” primary, which would earn them a spot in the general election and a chance to unseat Republican Rep. Dana Rohrabacher.

The ugly infighting has split the state Democratic Party from Democrats in Washington, who have watched in horror as the two candidates have gone after each other.* The fear is that the ongoing battle might sink both Democrats and allow Republicans to finish first and second on Tuesday, making the November election an all-GOP affair.

The accusations hurled around by Rouda and Keirstead have involved everything from Twitter “hacking” to harassment to fabricated university degrees. Both campaigns, in recent days, have told me stories about the other sending either staffers or private investigators to harass their volunteers, and each has denied the other’s story.

Narayana, for her part, has been a central player on both sides of this battle, after she jumped from Rouda’s campaign to become Keirstead’s political director last July. When Metcalf—a volunteer for Rouda—saw her holding the folder at the chili cook-off, she enlisted the help of another Rouda supporter to confront Narayana, who claimed that it was brought to her by someone else, and besides, there was no name on the folder. A confrontation with raised voices ensued, and eventually the folder was returned. (Narayana claims the folder was “ripped from my hands,” and she felt so harassed that she asked for an escort to her car.)

The allegations in the folder were less damaging than they seemed. A University of California at Irvine investigator had cleared Keirstead of any wrongdoing in the complaint, and it came out later that the “whistleblower” who filed it was a disgruntled former associate who was trying to sue Keirstead for $5 million in what Keirstead calls a “shakedown.” The associate eventually conceded in a court filing that, while he believed the allegations to be true at the time, they had later been proven “unfounded.”

But the allegations against Keirstead were enough to spook the Democratic Congressional Campaign Committee, which added Rouda to its “Red to Blue” program in May. The Keirstead campaign claims Rouda’s team had been shopping the allegations around since last year. (Rouda’s campaign denies this.)

The Keirstead campaign claims Metcalf had tried to dig up other dirt, too. She had sent Keirstead’s ex-wife, Melanie, a Facebook message on May 11 asking her about their divorce and raising the UCI allegations. “I hope there isn’t a mass coverup going on because we deserve better for our District and our country,” Metcalf wrote. Melanie passed the messages on to the Keirstead campaign, which argues Metcalf was “harassing” his ex-wife. (Metcalf rejected the idea it was “harassment.”)

Both Rouda and Keirstead have plenty of money to pounce on every allegation. (Self-funders are a common thread among leading Democratic contenders for coveted Orange County congressional seats.) Rouda has lent his campaign more than $1.3 million, while Keirstead has lent $725,000 to his. Keirstead won the endorsement of the California Democratic Party at the state convention earlier this year, and the state party didn’t appreciate the DCCC’s elevation of Rouda.

“When CDP Delegates endorse a candidate,” CDP Chairman Eric Bauman said in a statement, “that candidate is the official candidate of the Party, and the DCCC should tread carefully in openly supporting a different candidate.” He warned the DCCC that “attacks against our candidates coming from outside national groups will likely strengthen the resolve of our endorsed candidate’s supporters.” The DCCC has not spent against Keirstead, but a group backing Keirstead—314 Action, a political action committee supporting scientists running for office—has gone on the air against Rouda.*

The DCCC, Keirstead argues, went against him for a couple of reasons. When the UCI allegations surfaced, the DCCC told Keirstead to get the women mentioned in the complaint on camera to testify that it was unfounded, he said. Keirstead tried, but “all of them said no.” They’re in the midst of their careers and didn’t want to get involved. Keirstead understood. (A DCCC official said the group did not insist on-camera denials.)

Keirstead also thinks that Rouda was more eager to meet another of the DCCC’s typical requests: “cut big checks.” He said he’s willing to put more money into the race if necessary, but Rouda was willing to do it right away.

Rouda has tried to avoid becoming the nefarious “establishment” candidate, as a result of the DCCC endorsement, and he has touted his endorsements from progressive activist groups like Indivisible, the Sierra Club, and a wide swath of labor. His support of Medicare for All earned him the support of National Nurses United and the California Nurses Association. For someone who spent much of his life as a Republican—and a donor to Republicans—until relatively recently, Rouda has been able to consolidate a broad swatch of the Democratic coalition with surprising ease.

The panic over a Democratic lockout in Tuesday’s election probably encouraged some of that consolidation. This race, and the fear that the ballot in November will feature two Republicans, is the Democratic Party’s single biggest concern at the moment.

Keirstead, in an interview last week, suggested that Rouda must have an “unskilled” team, since his campaign is aiming so much of its fire at Rep. Dana Rohrabacher, when it really should be trying to bring down Scott Baugh, their main Republican competition for the second ticket out of Tuesday’s “top-two” primary. When I ran that comment by Rouda’s campaign manager, Mike McLaughlin, he countered with a litany of accusations of his own, that ranges from petty to grand.

At least Rouda’s supposedly “unskilled” team, he said, doesn’t put typos in its mailers. He also accused Keirstead’s team of “hacking” the Rouda campaign’s Twitter account—an allegation that also comes back to Narayana. When she switched sides last summer, she said, the Rouda campaign left her as an administrator on the Rouda account; when she recognized, she said, she got in touch with the Rouda campaign. Rouda’s team counters that they only noticed the problem when a pro-Keirstead message briefly appeared on their feed before being quickly deleted. It’s a sign of poor campaign management, Narayana argued, that they would forget to switch off their departing employees’ administrative functions.

Both Rouda and Keirstead, in my interviews with them, expressed dissatisfaction with the negativity in the race. Keirstead said this after half-an-hour of nearly uninterrupted accusations and counteraccusations against Rouda. Rouda, meanwhile, told me that he thought Democrats have spent too much time since 2016 focused on personalities rather than issues, when what politics is really about is “serving the greater good.”

When the interview with Rouda wrapped up, he asked me who else I’d interviewed. I told him Keirstead was coming later in the week.

“Don’t believe everything he tells you,” a staffer chimed in.

That wasn’t a problem in either case.

Corrections, June 4, 2018: Due to an editing error, this story originally misstated that the candidates had spent millions on attack ads. An earlier version of this article misstated the DCCC had spent opposing Keirstead’s candidacy.