In the days since Hillary Clinton lost the 2016 presidential election to Donald Trump, Bernie Sanders has been more present than ever on the political talk-show circuit. This is partly an effort to promote his new book, Our Revolution: A Future to Believe In, but it has also been an attempt to shed some light on just what went so terribly wrong for Democrats.

Sanders has not gone easy on them. The senator has called into question Hillary Clinton’s impulse to blame FBI Director James Comey for her loss and tweeted this week that he is “deeply humiliated” by his party’s failure to connect with white working-class voters.

“It’s been a tough week,” Sanders told The Late Show’s Stephen Colbert Monday night.

On the one question he has been asked the most since Election Day—“Could you have beaten Donald Trump?”—Sanders has been consistent in his refusal to answer the hypothetical, responding with some form of “Who knows?” Colbert did not ask him that question specifically, but he did want to know where common ground might exist between his supporters and those who voted for Trump.

“Above and beyond the incredible bigotry of the Trump campaign, what he did is he tapped into a lot of pain and anxiety and angst that the American people are feeling, which is very rarely reported in the media or understood by the punditry,” the senator said. While he never believed that Trump is a “hero of the working class of America,” Sanders said, “I hope I’m wrong.”

To those marching against Trump and sharing the hashtag #NotMyPresident, Sanders said, “I think people are expressing their feelings and exercising their constitutional rights,” but “what’s most important” is “to figure out where do we go from here” because “this is the reality.” The job of progressives now is to “figure out how we create an effective opposition.”

“The truth is, Democrats should not be losing to a candidate who insults so many people, who wants to give huge tax breaks to the top two-tenths of 1 percent and rejects climate change,” Sanders continued. “How are we losing these elections? Something is fundamentally wrong. What I am trying to do now is bring about structural changes in the Democratic Party so that it becomes a grassroots party.”

Asked by Colbert what an “autopsy” of the Democratic Party in 2016 would say, Sanders was quick to denounce the “liberal elite,” clarifying that he does not consider himself to be a part of that group despite his decades of experience in the U.S. Senate. He said the party must “transform” itself in order to “feel the pain of working-class people, of the middle class, of low-income people, of young people.”

“Trump’s views are a minority,” Sanders continued. “People do not think we should give tax breaks to billionaires. They do believe we should raise the minimum wage and have pay equity for women.” When people ask him what they should do now, he tells them to “get involved in the political process.”

“When millions of people stand up and fight back, we will not be denied,” Sanders declared to loud applause from the audience.

Finally, Colbert asked Sanders to lay out the best-case and worst-case scenarios for a Trump presidency.

“The best-case scenario is that Trump is not an ideologue,” Sanders said. “His views are all over the place,” he added, noting that the “good news” is that when millions of Americans press Trump on any given issue he just might listen to them.

Sanders did not sugarcoat the bad news. “The worst case, if not Trump himself, people around Trump are saying, hmm, ‘Let’s see, we’ve got the House, the Senate, we’ve got the White House, we’re going to have the Supreme Court, we’re going to change the rules of the game so we don’t lose anymore.’” If they can “unleash billionaires to buy elections, make it hard for millions of people to participate, they think they can control this government indefinitely.”

In an effort to not end on such a downer, Sanders reiterated that “our job is to bring tens of millions of people together to say, No. 1, this country is not an oligarchy—it’s a democracy. And No. 2, you’re not going to split us up by attacking our Muslim friends or our gay friends or women or anybody else. We’re going to stand together and fight for a government and an economy that works for all of us.”