Washington DC - Rep. Katie Porter, a Democratic star known for her incisive questioning of corporate leaders and use of a whiteboard to distill complex concepts in congressional hearings, announced Tuesday that she is running for the US Senate.

The Irvine, California, attorney is running for the seat widely expected to be vacated by Sen. Dianne Feinstein. The trailblazing San Francisco politician (89) was first elected to the Senate in 1992, but has faced questions in recent years about her mental fitness for office and has stepped back from some official duties. Her current term ends in early 2025.

"The threat from so-called leaders like Mitch McConnell has too often made the United States Senate the place where rights get revoked, special interests get rewarded, and our democracy gets rigged," Porter said in a video announcing her run. "Especially in times like these, California needs a warrior in Washington, and that’s exactly why I’m announcing my candidacy for the United States Senate in 2024."

Porter, a rising star in the Democratic Party, in November fended off a challenge from Republican Scott Baugh, a former state lawmaker, to secure her third term in Congress.

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Porter (49) was swept into Congress in 2018 as part of that year’s blue wave and quickly built a profile that extended beyond Orange County.

Her appearances at congressional hearings, wielding a white board and lobbing tough questions at corporate executives and Trump administration officials, repeatedly went viral. Her national notoriety became a fundraising juggernaut; she was one of the top House fundraisers this past election cycle.

Porter’s willingness to publicly confront party leaders, including former Speaker Nancy Pelosi, was an example of the determination that made Porter the surprise national standout of California’s 2018 House freshman class – and even early on stoked speculation of a future run for the US Senate.

Feinstein has said she does not plan to step down before her term ends, but has not announced whether she will run for reelection in 2024. She told the LA Times she would likely announce her intentions this spring.

However, Feinstein's retirement has been expected to prompt a wild and contentious race among California Democrats. The state’s deep bench of elected officials hoping to win higher office has largely been stymied by veteran politicians.

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More than four decades ago, Feinstein became mayor of San Francisco after former county Supervisor Dan White killed Supervisor Harvey Milk, one of the nation’s first openly gay elected officials, and Mayor George Moscone.

"I became mayor as the product of assassination," Feinstein said in an interview with The Times.

In recent years, her conservative policies wore on liberal Californians, including her vote for the Iraq war, support for the Patriot Act with expanded federal surveillance capabilities after the September 11 terrorist attack, opposition to single-payer healthcare, and her initial call for "patience" with Trump’s presidency.

Long viewed as one of the sharpest minds on Capitol Hill, Feinstein has recently faced allegations that her memory is slipping. She declined to become the Senate president pro tempore, a post historically awarded to the senior-most member of the majority party that puts the person third in the line of presidential succession.

In addition to Porter, other potential Senate candidates include Reps. Adam Schiff of Burbank, Barbara Lee of Oakland, Ro Khanna of Fremont, and Eric Swalwell of Dublin, as well as Los Angeles County Supervisor Holly Mitchell and former Oakland Mayor Libby Schaaf.

Schiff said he decided not to seek a leadership role in the House because of a potential Senate run.

"I was persuaded by many of my colleagues to consider running for the Senate if Sen. Feinstein decides not to run for reelection in two years, so I am exploring it," he told NBCLA in November.