Sen. Bernie Sanders, I-Vt., told Jordan Klepper on his Comedy Central show "The Opposition" that Donald Trump is "the worst president in the history of the United States."

The audience roared, but Sanders face remained serious. Klepper, who satirizes an alt-right, conspiracy-driven host, pushed back: "At least admit to him being the best at being the worst," he said.

"All right," Sanders replied. "I’ll grant you that."

Sanders is running for re-election in Vermont this year and emphasized the importance of the upcoming midterms. "It is imperative that we end one-party rule in Washington, where Republicans control the White House, the Senate and the House," he said.

Sanders added that 2018 is not about impeaching the president, but about "paying attention to the needs of working families in this country; stopping an agenda, which wants to throw up to 32 million people off of the health care they have, make massive cuts to medicare, medicaid, social security, disability, education and environmental protection — all the while, giving a billion dollars in tax breaks to the top one percent," he continued. "This election is among other things, stopping that agenda."

As a far-right parody, Klepper wasn't convinced. Why should he care? he asked Sanders.

"I think moving toward an authoritarian form of government, where you have a president who's a pathological liar," Sanders began.

"He's creative," Klepper interjected.

"He is creative in his lies, I do grant you that," Sanders conceded. "But they are lies, nonetheless. I think most significantly, this country has struggled with bigotry for several hundred years now. And we have made some progress in recent times, and to have a president who is trying to divide us up based on the color of our skin, or our gender, or our religion, or the country we came from — that is not what this country is about and we cannot allow that to continue."

The 12-minute conversation between Sanders and Kleeper was wide-reaching. They talked about income inequality and living wages, universal health care, North Korea and 2020.

Sanders did not confirm or deny if he is planning on running for president in 2020. "The focus right now is on 2018, 2020 is a way away and we'll make that decision at the appropriate time," he told Klepper.

Sanders also countered Klepper's claim that his candidacy would divide the Democratic party. "The truth is, there is less division among American people and certainly within the Democratic party than people think," he said. "For example, do people think we should give tax breaks to billionaires: Overwhelming opposition, people are unified in that. Do people believe we should have sensible gun safety legislation? The vast majority of the American people believe in that. Do people believe that women should earn the same amount of money doing the same work as men? Overwhelming support for that."

He continued, "Do people believe that climate change is real? Now, I know, you and the Donald think it's a hoax: emanating from China, I got it," Sanders assured Klepper, who was up in arms by this point. "But there are some of us who disagree with that suggestion."

In the end, Klepper offered his support to Sanders by pitching him some campaign slogans should he decide to run in 2020.