Sen. Bernie Sanders Bernie SandersButtigieg stands in as Pence for Harris's debate practice Bernie Sanders warns of 'nightmare scenario' if Trump refuses election results Harris joins women's voter mobilization event also featuring Pelosi, Gloria Steinem, Jane Fonda MORE (I-Vt.) on Thursday called President-elect Donald Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE a "pathological liar" who "changes his mind every single day."

"What do you do when you have a president-elect, soon to be president, who — and I say this not happily, but I think most people who observe him would agree — is a pathological liar who changes his mind every single day," the former presidential candidate said in an interview with MSNBC. The lawmaker then said that he hopes to see a new political movement of millions of Americans who "actually are following reality." ADVERTISEMENT "I am working very hard on this, and we need the help of the American people obviously ... to build a movement of millions of people who actually are following reality. And that's the challenge. Real change in this country, I am more and more convinced of it, is not going to come from Capitol Hill; it's got to come from grassroots America," he said.

"I want the truth. I really want to hear why people voted the way they voted. I want to hear why people voted for Donald Trump, what their expectations were, why they didn't vote for Secretary Clinton," he said.

"Second of all, I want to bounce off the people their views about what a progressive agenda is," Sanders added, stating that he wants to know if progressive policies are attractive to the working class.

Sanders has previously said he would be willing to work with Trump on strengthening the middle class but has remained critical about the president-elect's rhetoric.