Manigault Newman has made a number of claims in media appearances and in her new book, Unhinged, about the president making racist statements. She alleges tapes exist—and she has heard one—of him using the N-word racial epithet.

Trump denies any tape exists, and said he doesn’t use the N-word. The people that Manigault Newman said had played her the tape or had knowledge of it denied it. White House press secretary Sarah Huckabee Sanders said, however, that she couldn’t guarantee that no such tape exists, but that she’d never heard such a recording.

The president’s demand for arbitration is based on a confidentiality agreement that the Trump campaign states Manigault Newman signed with the organization covering her work on the 2016 campaign. Manigault Newman’s attorney said she hadn’t see any legal action filed as of earlier today and had no comment, according to NBC News.

Harder already represents Trump in California, where Stormy Daniels, the adult-movie actor, has sued him to nullify a non-disclosure agreement.

Harder has become widely known in recent years for suits brought by clients including Terry Bollea, known as Hulk Hogan, and Shiva Ayyadurai (an inventor who claims he invented email) against Gawker Media, the remains of which were sold to a division of Univision; Melania Trump, in a defamation lawsuit about the Daily Mail‘s claim that she had worked for an escort service (settled); and Ayyadurai against TechDirt, who alleged the digital policy editorial site had defamed him (dismissed, but being appealed).

After a jury found against Gawker, news emerged that billionaire Peter Thiel had helped fund Bollea’s lawsuit.