WASHINGTON — A day after Sen. Kirsten Gillibrand (D-N.Y.) called for President Donald Trump’s resignation in the wake of renewed sexual misconduct allegations, he fired back at her, claiming that she was once “begging” him for campaign contributions and that she “would do anything for them.”

He wrote, “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!”

A number of Trump’s critics immediately found his tweet itself a form of harassment and took it as suggestive innuendo about a female. Mika Brzezinski said on “Morning Joe” that its was “derogatory and disgusting.” Sen. Elizabeth Warren (D-Mass.) wrote on Twitter, “Are you really trying to bully, intimidate and slut-shame @SenGillibrand? Do you know who you’re picking a fight with? Good luck with that, @realDonaldTrump. Nevertheless, #shepersisted.” Rep. Jackie Speier (D-Calif.), also outspoken in on the issue of sexual harassment, called the tweet “grotesque.”

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

Gillibrand responded by writing on Twitter, “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.”

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, often mentioned as a 2020 presidential prospect, has been one of the leading voices on Capitol Hill in speaking out against sexual harassment and sexual misconduct. Last week, she was the first of Democrats in Congress to call for the resignation of Sen. Al Franken (D-Minn.), who was facing claims of unwanted sexual advances and groping. A cascade of senators followed Gillibrand in calling for Franken to step down. A day later, he announced that he would leave the Senate within weeks.

On Monday, three women who accused Trump of inappropriate behavior and sexual harassment reiterated claims they made during the campaign. It was part of a promotional tour for a new video short, “16 Women and Donald Trump,” that highlights 16 women who accuse Trump of sexual impropriety. He denies the claims.

Federal Election Commission records show that Trump gave Gillibrand $1,050 in 2007, when she was a member of the House of Representatives, and $4,800 in 2010, after she was appointed to the Senate.

Update: White House Press Secretary Sarah Huckabee Sanders defended Trump’s tweet and denied that it was sexual innuendo. “Only if your mind is in the gutter would you have read it that way,” she said.

“If you look back at past comments that this president has made, he’s used that same terminology many times in reference to men,” she said. According to an archive of Trump’s tweets, the only time he has used the phrase on Twitter has been in reference to Gillibrand.