A progressive group was quick to attack Rep. Adam Schiff after he announced his bid for California's U.S. Senate seat Thursday. 

Though Schiff has sought to position himself as a fighter against "MAGA extremists" and a champion of progressive values, the group laid into the longtime California congressman for his lack of accountability on former President Donald Trump

"Adam Schiff plays the role of Trump antagonist on TV, but a recent book details how he stalled and undermined leaders trying to hold Trump accountable in Congress. And he never challenges corporations or the Democratic establishment," Adam Green, co-founder of the Progressive Change Campaign Committee (PCCC), said Thursday in a statement. 

Schiff joins Rep. Katie Porter, D-Calif., in the competitive race for California's Senate seat held by Sen. Dianne Feinstein, 89, who is up for re-election in 2024. She has not announced re-election intentions.

CALIFORNIA DEMOCRAT REP. ADAM SCHIFF TO RUN FOR US SENATE SEAT HELD BY FEINSTEIN

Adam Schiff

Rep. Adam Schiff, D-Calif., joins Rep. Katie Porter, D-Calif., in the race for California's U.S. Senate seat. (Jonathan Ernst)

California Congresswoman Barbara Lee has said she intends to run for Feinstein's seat as well, but Lee has not made an official announcement. 

"When we should have gone big against Trump, Schiff said go small. When we should have gone fast, Schiff said go slow. And when bold leaders finally won consensus to pursue impeachment over Schiff's objections, Schiff leapt on stage to take credit," Green said in the PCCC's statement.

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The PCCC pointed to a recent book, "Unchecked: The Untold Story Behind Congress's Botched Impeachments of Donald Trump," as evidence of Schiff's complacency during the Trump administration. Porter, who announced her run earlier this month, has been endorsed by the PCCC. 

Katie Porter at campaign event

Rep. Katie Porter, D-Calif., speaks to supporters, volunteers and staff at an election night watch party at the Hilton Orange County Hotel in Costa Mesa, California, on Nov. 8, 2022. (Apu Gomes/Getty Images)

In Schiff's first interview since the campaign announcement, the California congressman said Feinstein is "more than comfortable" with Schiff's bid

"I wouldn't be doing that without that kind of blessing," Schiff said in reference to Feinstein during an appearance on Fox 11 in Los Angeles. 

Schiff's campaign website, launched Thursday, says "Adam has always championed progressive values and led the fight to protect our democracy."

"Our senator should work for Californians, not corporations," Porter said in a statement following Schiff's announcement. "I'm proud to be the only candidate who has never taken a dime of corporate PAC money."

It was an apparent dig at Schiff, her only declared opponent in the race, though her remarks did not call out Schiff by name. 

Adam Schiff and Kevin McCarthy

House Speaker Kevin McCarthy, R-Calif., right, recently removed Rep. Adam Schiff, D-Calif., from the House Intelligence Committee. (Tasos Katopodis)

Schiff did not immediately respond to Fox News Digital's request for comment.

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California uses a so-called jungle primary system in which the top two candidates in the primary advance to the general election, regardless of their party, making it possible for a potential Porter-Schiff showdown in the 2024 general election.