"He is a pathological liar," Sanders said. "This is not the kind of temperament we should have in the White House."
Sanders sat down with the hosts of ABC’s The View Wednesday ahead of his participation in the third Democratic debate, which will be hosted by ABC News in partnership with Univision in Houston on Sept. 12.
Sanders, who ran unsuccessfully in 2016 for the Democratic presidential nomination against former Secretary of State Hillary Clinton, told the hosts that that 2020 is different because "many of the ideas that I talked about," including universal health care, "were perceived to be radical," but now "a lot of candidates and the majority of the American people agree."
That progressive ideological shift, Sanders said, is what will help Democrats recapture the White House.
In recent polls, Sanders has performed behind former Vice President Joe Biden and close to Massachusetts Sen. Elizabeth Warren.
Sanders drew a contrast between himself and Biden, the front-runner, when asked to comment on the former vice president's campaign trail gaffes. He criticized Biden’s record on trade deals, the war in Iraq, and the bank bailout.
“Joe and I have our differences in terms of vision for the future,” Sanders said.
However, The View hosts pointed out that fellow presidential candidate, Sen. Elizabeth Warren espouses many of the same views -- a similarity that might make it difficult for him to distinguish himself. The lawmaker said that there is room for more than one candidate with similar stances in the Democratic field.
"Elizabeth is a friend of mine. She and I have known each other well over 20 years. She's going to run her campaign and I will run my campaign," Sanders said.
Still, Sanders, who said he has more than 1 million campaign volunteers, believes that his grassroots supporters will give him the edge he needs to secure the nomination.
The Vermont senator also said he was “not a great fan” of how the Democratic National Committee has hosted debates this campaign cycle. Sanders said he’d rather see single-issue debates with extended time to answer questions.
“Do it issue by issue rather than trying to deal with 50 different issues in a short period of time,” he said.
He also called for the elimination of superdelegates, delegates who are free to support any candidate at at the Democratic National convention and have in the past wielded powerful influence on who becomes the eventual party nominee. After 2016 the DNC changed the rules to limit the superdelegates' roles at the convention.
“I would ban superdelegates from voting on any ballot,” Sanders.
Sanders who often mentions taxing big corporations on the campaign trail was asked by The View’s Whoopi Goldberg, if he would make large companies pay more in taxes.
“Do you realize that if Facebook and Amazon and all the other gigantic corporations paid any tax, we could find some relief for regular Americans?” Goldberg asked.
“Of course, I'll change it,” Sanders replied. “I have been talking about it for 25 years.
"The function of a rational health care system is not to make billions for insurance companies and drug companies,” said Sanders at a campaign stop in Florence, South Carolina on Friday. “It is to provide health care to every man, woman, and child as a human right."
His plan has drawn criticism from his 2020 rivals including former Vice President Joe Biden and California Sen. Kamala Harris.
During his trip to South Carolina, Sanders teased an additional plan that would cancel $81 million in medical debt, prevent medical debt from negatively impacting credit scores and eliminate portions of the 2005 bankruptcy bill that make it more difficult to get rid of medical debt.
“Why should people be placed in financial duress? For what crime did you commit?,” Sanders told supporters in Florence, South Carolina. “You had a serious illness. That is not what this country should be about, but I think when we move to Medicare for All, we will end bankruptcy, and we will end families having to suffer financially.”
Sanders confirmed a more detailed plan on the topic is in the works.
“It is an insane cruel system that says you have to go deeply into debt or go bankrupt because of what?” Sanders told reporters. “Because they came down with cancer, they came down with heart disease, they came down with Alzheimer’s or whatever.”
This is the latest policy proposal from the Sanders campaign designed to tackle the rise of health care costs.
In July, Sanders took a trip to Canada to highlight the increasing prices of prescription drugs in the U.S.
In what was the first foreign trip of his 2020 presidential campaign, the senator joined a bus of diabetes patients on a drive from Detroit to Canada where the patients purchased insulin at prices that some said were 90% cheaper than what they would find in the U.S. The trip was inspired by a bus trip Sanders took two decades ago when he accompanied breast cancer patients into Canada to buy prescription drugs at similarly reduced prices.