“A lawsuit opens the door, and judges almost always allow for a plaintiff to have a fishing expedition”

David A. Super, a law professor at Georgetown University, said the lawsuit Ms. Clifford filed on Tuesday centered on a limited contract law matter, but he noted that it also specifically stated that Ms. Clifford would amend her complaint in the future to add the names of people who she said participated in wrongdoing with Mr. Trump and Mr. Cohen.

He suggested that Ms. Clifford and her lawyer might be starting with a narrow argument aimed at getting the contract declared invalid, perhaps intending to broaden it later to include claims that Mr. Trump and Mr. Cohen coerced her into silence. “If that happened,” he said, “they certainly could seek to depose Trump.”

And in that case, he said, “I can certainly imagine how it might get broader. And if it did, the wide array of Trump’s sexual interactions could be addressed, just as the wide array of Clinton’s sexual interactions was addressed in the Paula Jones case deposition.”