WASHINGTON – Democratic presidential candidate and Hawaii Rep. Tulsi Gabbard is suing 2016 Democratic nominee and former Secretary of State Hillary Clinton for defamation, escalating a feud between the two lawmakers after Clinton appeared to call Gabbard "a favorite of the Russians" last year.

In the lawsuit filed Wednesday in the U.S. District Court in Manhattan, Gabbard claims that Clinton made her remarks as "retribution" for the Hawaii congresswoman endorsening Sen. Bernie Sanders over Clinton in 2016.

"Clinton has not gotten over her loss in that election and still dwells on what happened," the lawsuit says, adding that "Clinton blames many persons for her loss," including Sanders. "But Clinton reserves a special hatred and animosity for Tulsi—who never endorsed Clinton, did not campaign for her, and to top it off, gave the nomination speech for Senator Sanders at the 2016 Democratic National Convention."

Asked to comment on the lawsuit, Clinton spokesman Nick Merrill told USA TODAY, “That's ridiculous.”

Gabbard in the lawsuit claims she has "suffered significant actual damages, personally and professionally, that are estimated to exceed $50 million—and continue to this day" because of Clinton's comments.

Clinton gave a wide-ranging interview on Democratic strategist David Plouffe's podcast in October, where she suggested that the GOP was "grooming" a Democratic presidential candidate to run as a third-party candidate. Although Clinton didn't name Gabbard specifically, the comment was seemingly directed to the Hawaii Democrat.

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"She's the favorite of the Russians, they have a bunch of sites and bots and other ways of supporting her so far, and that's assuming Jill Stein will give it up, which she might not, because she's also a Russian asset," Clinton said. "Yeah, she's a Russian asset, I mean totally. They know they can't win without a third party candidate."

Following Clinton's comments, Gabbard wrote in a tweet: "Great! Thank you @HillaryClinton. You, the queen of warmongers, embodiment of corruption, and personification of the rot that has sickened the Democratic Party for so long, have finally come out from behind the curtain."

Gabbard over the past several months has struggled to make the Democratic primary debate stage, missing both the December and January debates. . She has said she will not run for president as a third-party candidate.

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Contributing: The Associated Press