That’s where independent expenditure committees come in. Known as super PACs, these groups can accept unlimited contributions from those who want to exert more influence on voters by funding ads that can boost or attack their preferred candidate.

A handful of super PACs have spent more than $18 million on California’s Senate race so far and have at least $71 million more at their disposal. Super PACs have been formed to support all three Democratic front-runners — Reps. Adam B. Schiff of Burbank, Katie Porter of Irvine and Barbara Lee of Oakland. No similar group has appeared to support Republican front-runner and retired baseball player Steve Garvey.

Here’s a look at some of the biggest donors hoping to boost, or sink, Senate candidates in the primary election.

Cryptocurrency billionaires

Who they are: Silicon Valley leaders, including venture capitalists Marc Andreessen and Ben Horowitz; cryptocurrency executives Cameron and Tyler Winklevoss; cryptocurrency exchange Coinbase and its chief executive, Brian Armstrong
How much: At least $7 million against Porter
What’s their agenda: Candidates who support entrepreneurs “building the next generation of the internet”

A super PAC called Fairshake, funded by Silicon Valley billionaires and cryptocurrency investors, has launched an attack campaign against Porter. An advertisement that began airing in February makes no mention of crypto, instead painting Porter as a hypocrite who has railed against politicians who accepted corporate contributions while herself accepting more than $100,000 “directly from big pharma, big oil and the big bank executives.”

Fairshake is “standing up for California jobs and innovation,” the committee said in a statement. Porter has called the ads false, and decried the group as a “dark, shady super PAC.”

Fairshake has nearly $73 million on hand, federal filings show. That sizable war chest is critical for an industry that’s faced an avalanche of bad publicity after two of its best-known leaders faced criminal charges. FTX co-founder Sam Bankman-Fried, who was the second-biggest spender during the 2022 midterm election, was convicted on wire fraud and conspiracy charges in November. Former Binance Chief Executive Changpeng Zhao pleaded guilty to a money-laundering charge last year.

The founders of Andreessen Horowitz, one of Silicon Valley’s best-known venture capital firms, each contributed $7 million to Fairshake. A day after making the contribution, Horowitz wrote a blog post criticizing “misguided regulatory policy,” adding that if candidates want to “choke off important technologies, we are against them.”

Porter’s mentor, Sen. Elizabeth Warren (D-Mass.), has been one of Capitol Hill’s most skeptical voices on cryptocurrency. In 2022, Warren sent a letter to the authority that operates the Texas power grid, questioning the practice of paying crypto mining businesses for shutting off power and returning electricity to the grid during peak periods. Some companies reported earning more from the power grid subsidies than from crypto mining operations, she wrote.

Porter signed the letter, along with six other members of Congress, none of whom are in competitive primaries.

Patty Quillin and Quinn Delaney

How much: $1.5 million supporting Lee
Who they are: Philanthropists. Quillin is married to Netflix founder Reed Hastings. Delaney is married to real estate investor Wayne Jordan.
What’s their agenda: Criminal justice reform and lifting up Black and Latino candidates

In past elections, Quillin and Delaney gave millions to support criminal justice ballot measures in California and elect liberal district attorneys like Los Angeles’ George Gascón.

In this election, they funded a super PAC called She Speaks for Me, which ran advertisements in the fall spotlighting Lee’s long career in politics. Two of its top consultants quit after Lee criticized Gov. Gavin Newsom for saying he’d appoint a Black woman to the Senate if Feinstein died — but not any of the candidates already running in the 2024 Senate election, since that would provide an advantage.

The group has run some digital advertising for Lee in the run-up to the primary but has not had a huge presence.

Quillin and Delaney have a record of supporting candidates of color. Delaney has given Lee’s campaigns close to $50,000 since her first run for Congress. The three share a view that policies in California have been too harsh on people who commit certain crimes and that more money must be invested in communities of color.

Delaney and Quillin didn’t respond to requests for comment.

Hollywood workers

How much: Almost $450,000 supporting Schiff
Who they are: Directors, producers and labor unions
What’s their agenda: A senator who understands Hollywood

Donors with ties to Hollywood contributed almost $450,000 last year to the independent expenditure committee supporting Schiff, who has represented the area in Congress for nearly a quarter-century and counts many entertainment industry workers among his constituents. That includes contributions from Hollywood directors and producers, as well as more than $123,000 from the International Alliance of Theatrical Stage Employees union and its affiliated locals.

“If we couldn’t get behind Adam Schiff, I don’t know who we could get behind,” said Tyler McIntosh, the political and legislative director of IATSE, which represents more than 170,000 Hollywood crew members. “He’s really just been everything you could ask for in a champion.”

Schiff has worked for decades to protect California’s film industry and its workers, including leading an effort in 2020 to ensure that Hollywood workers could qualify for aid during the COVID-19 pandemic, McIntosh said. In 2021, Schiff helped organize a letter signed by 120 members of Congress urging the studios to return to the bargaining table after contract talks with IATSE broke down.

Schiff is “always willing to have a conversation, and to understand the issues,” said Alex Tonisson, the national executive director of IATSE Local 600, which represents more than 10,000 cinematographers, camera operators and publicists. The local doesn’t often give in support of specific candidates, he said, but Schiff deserves it.

If Schiff is elected to the Senate, McIntosh said, IATSE hopes he will be a champion on copyright, intellectual property and artificial intelligence issues, all of which have the potential to cut into members’ work and erode their residuals payments.

Carpenters unions

How much: $400,000 supporting Schiff
Who they are: United Brotherhood of Carpenters and the Western States Regional Council of Carpenters
What’s their agenda: More good union jobs

Schiff has received the endorsement of dozens of labor unions, but few are spending as enthusiastically as the carpenters union, which represents more than half a million workers.

A political action committee supporting Schiff, called Standing Strong, brought in $400,000 last year from two groups linked to the union: $250,000 from the political action committee funded and run by the national union and $150,000 from its Western chapter.

Standing Strong, the pro-Schiff PAC, has reported spending more than $9.1 million so far, mostly on ads that call Republican candidate Steve Garvey “too conservative for California.” The strategy could help boost Garvey’s profile among Republican voters and vault him into the general election. In a state where Democrats outnumber Republicans 2 to 1, Schiff’s path to election would be much easier if he faced Garvey — as opposed to Lee or Porter — in November.

John Hanna, the director of government and political affairs for the Western chapter, said the union supports Schiff because of his experience and his support for programs that help train and employ young people, including apprenticeship programs through labor unions. The national union declined to comment.

“We’re not doing this because we don’t like other people,” Hanna said. “It’s that we like Adam Schiff.”

In a state the size of California, where a successful advertising campaign in a major media market costs millions of dollars, the only way to make a meaningful difference is through independent expenditures, Hanna said. Otherwise, he said, the union would be limited to a single $5,000 contribution to Schiff’s campaign committee.

“This is the same amount whether it’s a state the size of California, or a state the size of Rhode Island,” Hanna said. “It’s the same $5,000. It’s not a realistic figure, in terms of what a campaign costs.”

Joseph W. Kaempfer

How much: $250,010 supporting Schiff
Who he is: Real estate developer and board chairman of the McArthurGlen Group, which develops designer outlet malls
What’s his agenda: Supporting Democrats who can be a bulwark against Trump

The 76-year-old was the largest individual donor last year to the super PAC supporting Schiff.

In an interview, Kaempfer said that he thought highly of the three Democrats running for the seat, but found Schiff to be the smartest and most effective.

Kaempfer, who donated $800,000 to groups supporting President Biden’s reelection, said he’s terrified about the prospect of President Trump returning to office. His support of Schiff is an extension of that fear. He said he wants senators who have experience going toe-to-toe with the former president.

“I want to have the strongest Senate we can have,” he told The Times. “I feel strongly that we should have good people in the Senate and in the House and that’s why I chose to do it.”

Gerald Singleton

How much: $250,000 supporting Porter
Who he is: Managing partner at Singleton Schreiber, a San Diego law firm
What’s his agenda: Changing tort and bankruptcy laws

The flood of outside money in this race has mainly focused on dinging Porter and boosting Schiff. A small effort has been mounted to support Porter from a group called OVRSITE PAC, a name that refers to the “OVRSITE” vanity plate on Porter’s Toyota Sienna minivan.

Singleton contributed $250,000, money that has gone into digital advertising.

Like Porter, Singleton is an attorney. His focus has been litigating cases related to wildfires. He recently was the lead attorney in a case against a Hawaiian power company after a wildfire swept through Maui. Singleton also led similar cases against Pacific Gas & Electric Company after fires in Northern California in recent years.

“I cannot think of a single issue that she is not on the right side,” he told students at a UC Berkeley School of Law discussion with Porter that was posted on YouTube. “She is exceptional.”

In an interview, the San Diego attorney said he had been wowed by Porter’s fluency on policy and her focus on issues such as housing. He said he gives money to state officials who support policy changes in areas such as tort reform and bankruptcy, which affect his business. But he is backing Porter because he’s a big fan.

He said he likes Schiff and Lee, and is a Padres fan, with fond memories of Garvey’s time as a first baseman in the 1980s.

“I just love Katie, and I think she brings something that we really don’t have in the Senate.”

Native American tribes

How much: $200,000 supporting Schiff
Who they are: Tribes that operate casinos in the Bay Area and Palm Springs
What’s their agenda: Legal sports betting at tribal casinos

The Agua Caliente Band of Cahuilla Indians, which contributed $100,000 to the pro-Schiff PAC last year, operates three casinos in the Palm Springs area. The tribe contributed more than $10 million to Proposition 26, the failed ballot measure that would have legalized sports betting on tribal lands. A representative for the tribe did not return requests for comment.

The front entrance to Agua Caliente Casino in Cathedral City, Calif.

(Mel Melcon / Los Angeles Times)

The Federated Indians of Graton Rancheria in the Bay Area also contributed $100,000 last year to the pro-Schiff PAC. Graton Rancheria operates the closest casino to San Francisco, near Rohnert Park, and has become a major donor to California politicians. The tribe contributed more than $30 million to the Prop. 26 campaign and has supported the campaigns of Gov. Gavin Newsom, Lt. Gov. Eleni Kounalakis and Atty. Gen. Rob Bonta. Newsom appointed chairman Greg Sarris to the UC Board of Regents last year.

A representative for the tribe declined to comment.

Wendy Munger

How much: $100,000 supporting Schiff
Who she is: Civic volunteer and retired attorney
What’s her agenda: Supporting Democrats

Wendy Munger comes from a famous Pasadena family that’s been active in both Republican and Democratic politics. Her father Charles Munger, the longtime investment partner of billionaire Warren Buffett, donated to the Huntington Library and Stanford University, among other philanthropic causes. He was a Republican, but Wendy has been a longtime donor to Democratic candidates, including Schiff and wrote a big check to the outside committee supporting him last year.

She’s also given money to the presidential campaigns of former President Obama and Secretary of State Hillary Clinton. Munger, who didn’t respond to requests for comment, has been supporting Schiff since he first ran for Congress in 1999, giving nearly $50,000 to his various campaigns through the years.