Ken Starr, former special counselor in the federal probe that preceded Bill Clinton’s impeachment inquiry, said that U.S. Ambassador Gordon Sondland’s testimony before members of Congress on Wednesday may prove a “game-changer” and—echoing what happened in 1974 to Richard Nixon—could cause Republican senators to head to the White House to urge President Donald Trump’s resignation.

Starr, now a Fox News contributor, made the remarks in an interview with the network’s “America’s Newsroom” in which he discussed his takeaways from Sondland’s opening statement, which had already been publicized.

“It looks as if there may be a bombshell or two in this and that’s what we’re looking for,” said Starr. “We’re looking to whether there is something that is a game-changer so we need to listen to [Sondland’s public testimony] very, very carefully.”

“Is he going to say those words, magic or otherwise ‘This was the deal’… however you describe it—a quid pro quo,” Starr said.

“The real issue is the senators are watching,” Starr continued. “Are senators going to now say, in light of what we hear today—it’s going to be a long day even with the ambassador alone—in light of what we have heard, ‘We need to make a trip down to the White House’—that historical example set during the Nixon presidency.”