IRVINE, Calif. — When some volunteers and organizers arrived Tuesday night at the University Synagogue, they found some orange and red pieces of paper on the chairs in the auditorium.

“NEGATIVE CAMPAIGN ALERT” read the paper in bold black letters. “The Dave Min campaign is running attack ads against multiple other Democrats! IS THIS WHAT ORANGE COUNTY WANTS?”

Organizers removed the papers, but they were literal signs of how tense the contest between Democrats in California’s 45th District primary has become.

Fifteen minutes into the candidate forum, Min was asked about ads aimed at his fellow University of California, Irvine law professor Katie Porter, and at Brian Forde, who worked for the Obama administration.

“There’s nothing in any of the ads that we launched that is false or a personal attack,” Min said, prompting some boos from the crowd.

“That is in sharp contrast to the three campaigns to my left who have been launching months and months of personal attacks, smear campaigns, character assassination,” Min said, gesturing to Porter, Forde and former congressional staffer Kia Hamadanchy, who were seated onstage with him.

Watch: California Primaries Packed With Democratic Candidates Hoping to Make the Cut

Democrats are targeting three other Republican-held districts that touch Orange County — the 39th, 48th and 49th. But those primary races have also taken a negative turn. Ask voters here about the contests, and they’ll often remark on the negativity, and how their mailboxes are stuffed with campaign materials.

While mudslinging in politics isn’t new, it’s a somewhat new experience for Orange County Democrats. For the first time in recent years, they have multiple viable candidates competing in an area long considered a Republican stronghold.

The question for Democrats is whether these contests have gotten too ugly — and if they could dampen the much-needed party enthusiasm heading into November.

A negative turn

Tensions between the Democratic candidates in the 45th District, held by GOP Rep. Mimi Walters, flared at the state party convention in February. Min secured the endorsement, but volunteers with the various campaigns reported heated exchanges with their opponents.

Last week, Min launched negative television ads and mailers. He criticizes two opponents in one ad: Porter for not being a licensed attorney in California (she is licensed in Oregon), and Forde for only switching his party registration from Republican to Democrat in 2016. (Forde has said he voted for Obama in 2008 and 2012.)

Min said his opponents have accused him of starting a whisper campaign aimed at Porter, targeting her divorce records. The rumors prompted Porter to tell her story to HuffPost. She said she took out a restraining order against her abusive husband, who then retaliated by saying Porter came at him.  a claim the judge dismissed, HuffPost reported.

Min and his wife, who works on domestic violence issues, released a lengthy statement denying he was behind the rumors. 

And he wasn’t the only one onstage addressing the negative turn during primary season.

The forum also hosted three Democrats running in the neighboring 48th District. Businessman Harley Rouda, who has been endorsed by the Sierra Club, was asked about a ThinkProgress story detailing his investments in crude oil-related stock.

Rouda said he had invested in an entity that bet on the price of oil, and he was no longer invested in that entity. He also said the information was being pushed by one of his opponents onstage with him, referencing stem cell researcher Hans Keirstead. 

Keirstead, in turn, was asked by a Rouda supporter whether he would release his personnel file from his time at UC Irvine, a question related to a Mother Jones report published Tuesday that detailed a series of allegations against him, including of affairs with students and that he punched a female student outside a nightclub. The university investigated the incident and determined the claims were unfounded.

Keirstead said in an interview at his biomedical company in Irvine that he has armed his campaign staffers with “fight-the-smear toolkits” to respond to questions about the lawsuit. He said he expected the issue to come up in the general election should he face GOP incumbent Dana Rohrabacher, but was surprised it was an issue in the primary. 

In the 39th District further north, negativity between Navy veteran Gil Cisneros and health insurance executive Andy Thorburn prompted the state party and the Democratic Congressional Campaign Committee to intervene.

The party organizations brokered an agreement between the two last week to refrain from attacking each other ahead of the June 5 primary, where Democrats run the risk of not advancing to November. Under California law, all candidates run on the same ballot, and the top two vote-getters, regardless of party, advance to the general election.

And moving south to the 49th District, environmental lawyer Mike Levin, also endorsed by the Sierra Club, has been forced to respond to claims from fellow Democrat Paul Kerr. A section at the top of Levin’s campaign website is titled “Paul’s False Claims,” in which Levin counters charges that he is a lobbyist who supports drilling to access natural gas. Levin, Kerr and Marine veteran and 2016 Democratic nominee Doug Applegate did not respond to requests for comment.

Sara Jacobs, a fourth Democrat running in the 49th District, said the party should be focused on Republicans and President Donald Trump.

“The Democratic candidates who are attacking other Democrats are just doing the Republicans a big favor right now,” she said in a statement.

Long-term impact?

The question for Democrats in these races is whether the nastiness of the primaries will weaken the party’s efforts in the general election —  especially in an area where every ounce of Democratic energy is needed.

Orange County is traditionally Republican territory. Hillary Clinton was the first Democratic presidential nominee to win the county since Franklin D. Roosevelt in 1936. But while voters backed Clinton, they also supported area GOP lawmakers in 2016. While Democrats say this part of Southern California is shifting away from its Republican past, they acknowledge that hard work is ahead for the candidates trying to flip some of these seats.

So with the primary campaigns becoming more divisive, will opposing candidates’ supporters still be willing to donate, knock on doors, and make phone calls for the eventual winner?

Deborah and Wyatt Carr, a couple volunteering with Porter’s campaign who attended her town hall meeting at a Laguna Woods retirement community on Saturday, said they would reluctantly vote for Min if he wins the primary.

Johanne Kaminski, a passionate Min supporter, said after the Tuesday night forum that she was concerned the negative environment (which she attributed to Porter’s campaign) would hurt Democratic unity after the primary. Kaminiski said that should Porter win the primary, she would volunteer with the local county party or state legislative candidates, rather than Porter’s campaign.

But the candidates and grass-roots leaders are confident Democratic voters will coalesce around the eventual nominee, despite the divisive primaries

“We may not all exchange Christmas cards at the end of this, but I hope that everyone in this race has the same goal and remembers the same goal, that this is about beating Mimi Walters at the end of the day,” Min said in an interview at a canvass launch in Lake Forest on Sunday. He said he would publicly endorse and support the winner of the primary “to the best of my abilities.”

Keirstead was also not concerned about decreased energy on the ground, and also said he would back Rouda even though he believed his opponent was circulating information about the lawsuit to reporters.

Rouda, for his part, was hopeful Democrats would come together.

“I know that people think that’s a concern,” he said of lingering Democratic divisions after the primary. “But everybody’s been very committed to whoever the Democratic candidate is that advances … And ultimately, whoever emerges is a better choice than Dana Rohrabacher.”

Marian Bodner, the leader of Indivisble CA39, also doubted that hard feelings from the primary would deflate her group’s passionate members, leaving them less engaged if their preferred candidate did not win.

“I think we all feel like there’s just way too much at stake to give up or be turned off just because of that,” she said.

Correction 1:22 p.m. | An earlier version of this story misindentified the target of allegations mentioned in a Mother Jones story published Tuesday.