Mr. Schiff, who led the first impeachment trial of President Donald J. Trump and later served on the House panel investigating the Capitol riot, will seek the seat held by Senator Dianne Feinstein.
Representative Adam B. Schiff became one of the most prodigious fund-raisers in Congress during the presidency of Donald J. Trump.
WASHINGTON — Representative Adam B. Schiff, the California Democrat who emerged as one of President Donald J. Trump’s chief congressional tormentors from his perch atop the House Intelligence Committee, announced on Thursday that he would seek the Senate seat long held by Dianne Feinstein.
“I wish I could say the threat of MAGA extremists is over,” he said in a video on Twitter. “It is not. Today’s Republican Party is gutting the middle class, threatening our democracy. They aren’t going to stop. We have to stop them.”
Mr. Schiff, 62, is the second member of California’s Democratic congressional delegation to join the 2024 race, after Representative Katie Porter. He enters the campaign with the largest national profile, built from his position as the manager of Mr. Trump’s first impeachment trial. He later served on the House committee responsible for investigating the origins of the Jan. 6, 2021, attack on the Capitol.
On Tuesday, Speaker Kevin McCarthy, a Republican, exiled Mr. Schiff and Representative Eric Swalwell, another Democrat, from the House Intelligence Committee in retribution for their actions toward Republicans when Democrats held the majority.
Ms. Feinstein, 89, has not said whether she will run again in 2024 but is widely expected not to do so as she faces Democratic worries about her age and ability to serve. Last year, she declined to serve as president pro tem of the Senate, and in 2020 she ceded her post as the top Democrat on the Senate Judiciary Committee after coming under pressure from her party during the Supreme Court confirmation hearing of Justice Amy Coney Barrett.
A former federal prosecutor, Mr. Schiff served in California’s State Senate before being elected to a Los Angeles-area House seat in 2000.