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She’s running.

Trump, who has been accused of sexual misconduct by 19 women, lashed out on Twitter at New York Senator Kirsten Gillibrand, a leading voice against sexual harassment on Capitol Hill, calling her a “flunky for Chuck Schumer” who was “very disloyal” to Bill Clinton and “Crooked” Hillary Clinton. He also wrote that Gillibrand, a Democrat, had previously come to him “begging” for campaign donations and, in a sexually suggestive formulation, “would do anything for them.”

Not only does Trump call Gillibrand a “lightweight,” but underscores her supposed subservience by suggesting she solicited favors from three males—Schumer, Clinton, and Trump himself. Gillibrand later called it “a sexist smear.”

Sensing an opportunity, Gillibrand fired back shortly after, asserting that Trump could not “silence me or the millions of women” who have spoken out against the president.

Ironically for Trump, his feud with the Democrat has only raised her status as a leading member of the opposition and an important voice against sexism on the national political stage. Gillibrand was the first Democratic senator to call for Al Franken’s resignation, following multiple allegations of sexual misconduct. A member of the Armed Services Committee, she also led the charge against sexual assault in the U.S. military.

On Monday, she officially hopped on Trump’s bad side, when she called for Trump’s “immediate” resignation in light of the many sexual assault and misconduct allegations against him. “These allegations are credible; they are numerous,” said Gillibrand. “I’ve heard these women’s testimony, and many of them are heartbreaking.”