Former President Bill Clinton issued a veiled criticism of President Trump on Monday, saying one’s “ability to bad-mouth” another person isn’t “evidence of authenticity.”

“I don’t believe your ability to bad-mouth somebody else is evidence of authenticity,” Clinton said during a speech Monday at Georgetown University.

Trump has been praised by his supporters for rebuffing political correctness and offering brash and blunt attacks on critics.

Clinton delivered a wide-ranging speech at an event marking the 25th anniversary of his election in 1992, during which he lamented the polarization of the country and urged Americans not to reward politicians who sow division.

“This us-versus-them thing is the most dangerous thing we’re confronting,” the former president said. “But as long as it’s rewarded politically, it will continue.”

Clinton said the political climate today is more polarized than when he was elected more than two decades ago, and said it’s difficult for him to imagine Congress passing a federal ban on assault weapons as they did during his presidency.

The former president said that while some politicians may be able to win elections by dividing the American people, it’s an ineffective long-term strategy.

“You can win more elections in the short run when people are mad with subtraction and division, but it’s a lousy way to run a railroad,” he said. “You won’t build much that lasts that way.”