Progressives are seeking to mount a Democratic primary challenge to Sen. Dianne Feinstein (D-Calif.), who said she will pursue re-election to a sixth term in 2018.

Top California Democrats quickly endorsed Feinstein’s bid, including House Minority Leader Nancy Pelosi and Sen. Kamala Harris. Harris already has begun raising money for the senior senator’s re-election.

Feinstein’s critics on the left, however, pounced. Rep. Ro Khanna, a progressive Democrat who represents Silicon Valley, called Feinstein “out of touch” with the grassroots on issues like the economy and foreign policy.

“The fact that the establishment is rallying around her re-election shows that DC insiders continue to privilege protecting one of their own over the voters’ concerns,” Khanna, a freshman in Congress, said on Monday.

Khanna said he won’t challenge Feinstein himself. He told Politico that he has contacted liberal Democrat Rep. Barbara Lee and former Secretary of Labor Robert Reich, urging them to run instead.

Feinstein, 84, a former San Francisco mayor who has served in the Senate since 1992, would be 91 at the end of her prospective term. “Lots more to do: ending gun violence, combating climate change, access to healthcare. I’m all in!” Feinstein tweeted Monday in announcing she’ll run for re-election.

Feinstein drew the ire of progressives in August after expressing hope that Donald Trump could “be a good president” and arguing he “can learn and change” with “patience.” Her comments didn’t play well in California, where the liberal Trump “resistance” movement is especially active.

Feinstein also has irked progressives on health care, which is quickly emerging as a litmus test in the Democratic Party. While she supports a public option for health insurance, she has been hesitant to embrace single-payer health care because of its large price tag.

Other potential primary challengers to Feinstein in 2018 include California Senate President Pro Tem Kevin de León, who is Latino. De León has not yet announced whether he will run.

The New York Times reported that Feinstein declared her bid for re-election this week because an announcement from de León was “imminent.”

Markos Moulitsas, publisher of Daily Kos, a liberal blog that raises funds for progressive candidates around the country, cheered a possible de León candidacy on Twitter.

“We share a common interest in this Senate race. Let’s beat the most pro-Trump Blue-state Dem in the country!” Moulitsas tweeted Monday.

Wealthy California entrepreneur Joseph Sanberg, another potential challenger in the Senate race, took to Twitter to tweak Feinstein for her comments about working with Trump.

“California deserves a bold progressive fighter who will stand up to Trump – bullies like Trump are defeated by courage, not patience,” Sanberg wrote. “More important than ever that all CA’s representatives in DC lead not appease ― at stake are those lives of Californians struggling!”

Feinstein dismissed talk of a primary challenge on Tuesday, maintaining she is “the best person” to challenge the Trump administration’s policies on issues like immigration, health care, women’s rights and the environment.

“I’m not interested in sparring with fellow Democrats, I’m interested in defending California against President Trump’s repeated attacks against our state,” she said in a statement.

Any Democrat who runs against Feinstein will face a formidable challenge. Her campaign reported nearly $3.6 million cash on hand in June, a significant advantage in California’s expensive media market. She is an experienced politician, and much of the Democratic establishment backs her.

This story has been updated with Sen. Feinstein’s statement.