In its 44-page response filed in New York State Supreme Court, Fox argues that the claims of electoral fraud made on its channels by Mr. Trump’s lawyers — including Rudolph W. Giuliani and Sidney Powell, who are also named in the defamation suit — were matters of significant interest to viewers and handled fairly.

“This lawsuit strikes at the heart of the news media’s First Amendment mission to inform on matters of public concern,” Fox says in the motion, adding, “An attempt by a sitting president to challenge the result of an election is objectively newsworthy.”

Paul D. Clement, a partner in the Washington office of the law firm Kirkland & Ellis who served as solicitor general under President George W. Bush, is leading Fox’s defense. “Smartmatic’s theory is fundamentally incompatible with the reality of the modern news network and deeply rooted principles of free speech law,” Mr. Clement said in a statement.