The conservative Republican made the surprising comments — after months of taking care not to trash the Democratic presidential front-runner — in a wide-ranging New York Post editorial-board interview.
Asked whether Americans are ready to elect Rudy Giuliani — a leader, the questioner noted, whom Ed Koch had called a "nasty man" — Gingrich shot back, "As opposed to a nasty woman?"
Gingrich added that he thinks she'll be the nominee, and cited the battle between Clinton's camp and Sen. Barack Obama's team last week over Obama donor David Geffen bashing the former first couple.
"Nobody will out-mud the Clintons," said Gingrich, who added that he'll decide in the coming months whether to run for the White House.
He called Clinton's political team one of the most "talented" in U.S. history, but "endlessly ruthless."