Sen. Kirsten Gillibrand of New York called on President Donald Trump to resign over the many accusations of sexual assault that have come to light in the last year. Trump’s response Tuesday morning was to send a tweet loaded with sexist accusations, including that she is a “lightweight,” “flunky,” and wiling to “do anything” for campaign donations.

Trump has, indeed, donated to a number of Democrats in the past, including Schumer, former Rep. Anthony Weiner, Hillary Clinton, and Gillibrand, to whom he gave $4,800 as recently as 2010.

Lightweight Senator Kirsten Gillibrand, a total flunky for Chuck Schumer and someone who would come to my office “begging” for campaign contributions not so long ago (and would do anything for them), is now in the ring fighting against Trump. Very disloyal to Bill & Crooked-USED! — Donald J. Trump (@realDonaldTrump) December 12, 2017

Trump’s implication that Gillibrand would “do anything” for a donation stands out as the kind of loaded comment that can intimidate women from calling out sexual misconduct.

This reads like sexual harassment. @SenGillibrand calls for him to be disciplined, and he implies, well, exactly what “and would do anything for them” implies. https://t.co/1jVsExFJHI — Jamil Smith (@JamilSmith) December 12, 2017

Gillibrand fired back with her own defiant tweet.

You cannot silence me or the millions of women who have gotten off the sidelines to speak out about the unfitness and shame you have brought to the Oval Office. https://t.co/UbQZqubXZv — Kirsten Gillibrand (@SenGillibrand) December 12, 2017

Gillibrand has emerged as a leading advocate for reform on sexual assault and harassment issues in the Senate. Gillibrand has made efforts to address sexual assault in the military and on college campuses. She led the campaign that ultimately ousted Sen. Al Franken.

She’s renewed her attacks on Trump in recent days, too, as Democrats try to position themselves as the party against sexual misconduct, in contrast to Republicans who haven’t called for an investigation into Trump and who have largely supported Alabama Senate candidate Roy Moore.

“President Trump has committed assault, according to these women, and those are very credible allegations of misconduct and criminal activity, and he should be fully investigated and he should resign,” Gillibrand told CNN’s Christiane Amanpour on Monday.

Trump refuted renewed claims of sexual misconduct against him in a tweet this morning.

Since Gillibrand called on Trump to resign, Sens. Ron Wyden (D-OR), Cory Booker (D-NJ), Jeff Merkley (D-OR), and Bernie Sanders have also echoed the call. Also on Monday, more than 50 female Democratic lawmakers asked the House Oversight Committee to investigate the allegations against Trump in a letter to committee Chair Rep. Trey Gowdy (D-SC) and ranking member Rep. Elijah Cummings (D-MD).

Gillibrand made headlines in November when she said in an interview with the New York Times that former President Bill Clinton should have resigned in light of the Monica Lewinsky scandal in the 1990s. “Yes, I think that is the appropriate response,” she said when asked whether Clinton should have stepped down at the time.

The remarks appear to be what Trump was referring to in his tweet that she was “disloyal to Bill & Crooked.” Gillibrand holds Clinton’s former Senate seat.

In her November interview with the Times, Gillibrand said that had the Clinton scandal taken place today, there “should be a very different reaction” and turned her attention to President Trump, who has been accused of sexual misconduct by more than a dozen women and was caught on an Access Hollywood tape bragging about sexually assaulting women.

“I think in light of this conversation, we should have a very different conversation about President Trump, and a very different conversation about allegations against him,” she said.