In an appearance on Real Time With Bill Maher last night, Bernie Sanders expressed frustration at “tough guy” Donald Trump backing out of his agreement to have a televised debate with him, and discussed some strategies for beating Trump in November’s general election.

Earlier this week, Trump had agreed to debate Sanders before the June 7th California primary for 10 million dollars to be given to charity, and though triple that money was raised and offered by multiple broadcast television networks, Trump today reneged on his agreement. Sanders groaned loudly and shook his fists when Maher asked about the presumptive Republican nominee’s withdrawal from the hotly-anticipated debate and said he “would have loved to” have the debate and hoped Trump would flip-flop again and agree to it.

“First he said he would do it,” Sanders said. “Then he said he wouldn’t do it. Then he said he would do it. Then he said he wouldn’t do it. So I would hope that if he changed his mind four times in two days, [he’d] change it a fifth time. You know, Trump claims to be a real tough guy, pushes people around. Hey, Donald, come on up. Let’s have a debate about the future of America.”

Bernie Sanders and Bill Maher agree: ‘Tough guy’ Donald Trump ‘chickened out’ of debate https://t.co/997ThgkhmP — Post Politics (@postpolitics) May 28, 2016

Sanders went on to agree with Maher that Trump is a “crazy person,” and said that he would be a “danger to the world” if he was allowed to become President.

“This guy is a pathological liar,” Sanders exclaimed. “I don’t want to be malicious, but that’s just the damn truth. He would be a real embarrassment, a real danger to this entire world if he became president.”

Maher also brought up the State Department agency audit that turned up the heat on Hillary Clinton’s ever-worsening email scandal, which Sanders has been famously reluctant to attack her on. Last night was no different, with Sanders opting instead for general statements about voters’ attitude toward the state of politics as usual in America, despite Maher’s pointing out that the audit means “the story has moved a little bit” since the beginning of the primary race.

“There is enormous frustration on the part of the American people with the way we do politics in this country,” Sanders said. “And what most politicians do is say, ‘I’m great; you’re terrible. Vote for me; the other guys are scum of the earth. Blah, blah, blah, blah.’ But, you know what? People are hurting in this country. Our middle class is disappearing. We’ve got a lot of poverty. We don’t have health care for all people. People want us to talk about their lives and their issues and not just spend our whole lives attacking our opponents.”

WATCH: Bernie Sanders and Bill Maher Talk About the Canceled Trump Debate and More https://t.co/nH1GtJ4ox9 (VIDEO) pic.twitter.com/d0J447DBmJ — Mediaite (@Mediaite) May 28, 2016

Sanders showed no such reluctance to go on the attack repeatedly against Trump, however, as Maher pressed with questions about how Sanders would go about beating him in November’s general elections after pointing out that he’s been polling much better against Trump than Clinton has. He repeatedly took shots at the business mogul’s inconsistency in his political positions, his hotly controversial remarks about Mexican immigrants, Muslims and women, and his proposed tax breaks for the wealthy.

“That is a good question, and I would not be honest if I told you I’ve figured it out yet,” Sanders replied. “He is so unpredictable because he lies all of the time — not a joke. He changes his mind all the time.”

Sanders mused that a good first step might be to point out how deeply proud Americans are of their cultural diversity, and how “the vast majority of Americans are not happy with” Trump’s rhetoric against Latinos, Muslims and women. Sanders also pointed out how Trump is “primarily a showman” and a “very good manipulator of the media,” but that his ideas on public policy are “absurd.”

“Giving hundreds of billions of dollars in tax breaks to the top two-tenths of one percent is not particularly good public policy,” he continued.

[Photo by Alex Wong/Getty Images]