Lindsey Graham says Comey will testify before a Senate committee the day after the first presidential debate.

Senator Lindsey Graham, Republican of South Carolina and chairman of the Judiciary Committee, said Wednesday night that James B. Comey, the former F.B.I. director, would testify before the committee on Sept. 30 without a subpoena.

“The day of reckoning is upon us when it comes to Crossfire Hurricane,” Mr. Graham told the Fox News host Sean Hannity, referring to the internal code name for the 2016-17 F.B.I. investigation into the Trump campaign’s ties to Russia.

“I appreciate Mr. Comey coming before the committee,” Mr. Graham said. “He will be respectfully treated, but asked hard questions.”

The testimony would be one day after the first of three debates between President Trump and Joseph R. Biden Jr., and three days after Showtime begins airing “The Comey Rule,” the miniseries adaptation of “A Higher Loyalty,” Mr. Comey’s best-selling book.