President Trump claimed Tuesday that Sen. Kirsten Gillibrand, D-N.Y., used to be willing to "do anything" in exchange for his donations to her Senate campaign, before she turned on him and started calling for him to resign over sexual harassment accusations.

"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!" Trump tweeted Tuesday morning.

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



Related: Kirsten Gillibrand fires back at Trump

Gillibrand has joined other Democrats who have said Trump needs to step down after several women reiterated their claims that Trump sexually harassed them. On Monday, three of his accusers appeared on NBC's "Today with Megyn Kelly" to discuss Trump's inappropriate sexual advances.

In response, Gillibrand called on Trump to resign.

“These allegations are credible, they are numerous,” Gillibrand told CNN. “I’ve heard these women’s testimony, and many of them are heartbreaking. President Trump should resign his position.”

Gillibrand was joined in her call by other Senate Democrats, who say that because Sen. Al Franken, D-Minn., resigned over similar charges, Trump must also step down. Democrats Cory Booker of New Jersey, Jeff Merkley of Oregon, and Ron Wyden of Oregon have said Trump should step down, as well as Independent Sen. Bernie Sanders of Vermont.