Sen. Bernie Sanders (I-VT) over the weekend said he fears that if Democrats nominate former Vice President Joe Biden in 2020, President Donald Trump will defeat him like he did Hillary Clinton in 2016 because voters will not be excited about Biden and his candidacy.

Cenk Uygur of “The Young Turks” program asked Sanders if Democrats are on the verge of “making the same mistake that it did in picking Hillary Clinton, who lost to Donald Trump.”

“I fear that it could be, I really do. I fear that you would have a campaign without a lot of energy and excitement,” Sanders replied, according to a Sunday RealClearPolitics transcript. “Could Joe beat Trump? Yeah, I think he could. I’m not saying he can’t. But I think we don’t want to make the same mistake that we made last time. And sometimes this is where the establishment talks to itself.”

Sanders also took issue with the establishment’s conventional wisdom that Biden is the Democrat best positioned to win the Rust Belt states, arguing that Biden’s past support for NAFTA, bad trade deals with China, and the Iraq War will turn off a lot of voters in the Midwest who voted for Trump because they liked his economic nationalism and America-first foreign policy.

“And why do I think we can do a good job in defeating Trump? Because in the issues that Trump beat Hillary Clinton on–trade, you go to the Midwest and say, ‘I voted for NAFTA, I voted for permanent normalized trade relations with China.’ Which is what Joe Biden did, you think that’s going to resonate terribly well in the Midwest? I don’t think it will. I lead the opposition against those disastrous trade agreements,” Sanders said. “You think going around the country and telling people, ‘I voted for the war in Iraq,’ which is what joe did. Think that’s going to resonate well with people? I don’t think so. It was probably the worst foreign policy blunder in the modern history of this country. I led the opposition to the war in Iraq. For those reasons, nationally and especially in the battleground states, we are the campaign that could rally young people, working people, people of color, to win this election.”

Sanders then called out Democrats for ignoring the needs of working-class Americans, saying the party needs to understand that getting rid of Trump will not rid the forces that got someone like Trump elected in the first place.

“What was that? It is because for too long the Democratic establishment has ignored the needs of working people all over this country. People work longer hours for lower wages—40 million people living in poverty. The only major country not to guarantee health care to all people as a right,” Sanders continued. “A vigorous effort to combat climate change, dealing with criminal justice reform, immigration reform. Those are issues that are not only the major issues facing this country, income and wealth inequality — how do you not talk about that? We have got to talk about that because it is the right thing to do and it is the way you win an election.”

Biden, who is far from where the energy is on the left in today’s party and has not drawn big and enthusiastic crowds at his campaign events, has taken a commanding lead in nearly every state and national poll because Democrats think he is their best candidate against Trump.

While kicking off his campaign in Philadelphia, Pennsylvania, Biden previewed what may become his best and go-to argument as the campaign season heats up, saying that Democrats will have no chance of getting any progressive policies enacted if they first do not beat Trump.

“The first, most important plank in my climate proposal is, beat Trump. Beat Trump, beat Trump,” Biden said.

Democrats on the left who support candidates like Sanders and Sen. Elizabeth Warren (D-MA) argue that Biden is not “woke” enough on a variety of economic and racial justice issues to inspire voters on the left to not only vote for him but to volunteer their time to convince others to do so. Biden’s backers, on the other hand, have been making the case to primary voters that Trump the president will be the best organizing tool for Democrats in 2020.