LOS ANGELES — Former Democratic U.S. House member Katie Porter announced Tuesday that she is entering the 2026 contest for California governor, joining a crowded field of candidates that could be upended if former Vice President Kamala Harris joins the race.

Porter, who became a social media celebrity by brandishing a white board at congressional hearings while grilling CEOs, promised in a campaign launch video to be an aggressive counterweight to President Donald Trump’s administration at a time when the heavily Democratic state has clashed with the White House over issues from water management to immigrant rights.

“In Congress, I held the Trump administration’s feet to the fire when they hurt Americans. As governor, I won’t ever back down when Trump hurts Californians — whether he’s holding up disaster relief, attacking our rights or our communities, or screwing over working families to benefit himself and his cronies,” Porter said.

Large Group of Potential Candidates for Newsom’s Seat

The contest to replace term-limited Democratic Gov. Gavin Newsom already has lured a large scrum of announced and likely candidates that would be upended if Harris decides to seek the state’s top office.

Harris, a former state attorney general and U.S. senator, has not ruled out seeking the governorship since she left Washington in January after a failed presidential bid. Porter is friendly with the former vice president and has indicated she would step aside if Harris joins the race. In 2012, Harris, then California’s attorney general, appointed Porter to be the state’s independent bank monitor in a multibillion-dollar nationwide mortgage settlement.

If Harris gets in the race “there are very few politicians who would want to take her on,” said Claremont McKenna College political scientist Jack Pitney. “She’d be likely to win the Democratic nomination and Democrats are likely to win the governorship.”

Porter, who made an unsuccessful run for U.S. Senate last year and also is known for her small-dollar fundraising prowess, becomes one of the best known candidates, joining former Los Angeles Mayor Antonio Villaraigosa and Lt. Gov. Eleni Kounalakis, among others, on the Democratic side.

Democrats are expected to easily hold the seat in a state where they outnumber registered Republicans by nearly 2-to-1. Republicans have not won a statewide election in California in nearly two decades.

The GOP Has a Major Candidate

On the GOP side, Riverside County Sheriff Chad Bianco last month became the first major Republican to announce a bid to replace Newsom, whose term runs through early January 2027. He blamed Democrats for the ongoing homeless crisis and runaway housing prices.

Bianco responded to Porter entering the race saying, “Katie Porter is a failed progressive Democrat with a history of supporting policies that increased inflation, grocery, gas and energy prices. She is cut from the same cloth of the failed career politicians who created California’s cost-of-living crisis. We cannot expect the same people who created this mess to get us out of it. Californians deserve so much better.”

Even if Harris gets in the race, the state’s open primary system can be unpredictable — all candidates appear on a single ballot, regardless of party, and only the top two vote-getters advance to the November general election. Trump-aligned candidates could enter on the GOP side, generating conservative interest, or a wealthy candidate could emerge with the funds to rattle the expected order.

“These open primaries are hard to handicap,” said Democratic consultant Andrew Acosta. “It just makes it harder to predict.”

Porter, a progressive favorite, created an online backlash after losing the 2024 Senate race, when she faulted “billionaires spending millions to rig this election.” She finished third in the primary — behind Democrat and now-Sen. Adam Schiff and Republican Steve Garvey — and did not advance to the November election.

Some likened her words to Trump’s baseless claims of election fraud in 2020. Porter later clarified her initial statement to say she didn’t believe the California vote count or election process had been compromised but she didn’t recant her earlier remarks. Rigged, she said in a follow-up, “means manipulated by dishonest means.”

She has been an active fundraiser since leaving her Southern California House district in January and returned to teaching at the University of California, Irvine, School of Law.

A consumer protection attorney before her election to the House, Porter became known in Congress for her unsparing interrogations of business leaders and other committee witnesses, often using her whiteboard to break down complex figures while using plainspoken language to assail corporate greed.

First elected to Congress in 2018, Porter said in her video that “I first ran for office to hold Trump accountable. I feel that same call to serve now to stop him from hurting Californians.”

(GV Wire’s Anthony W. Haddad contributed to this article)