During an MSNBC town hall with Chris Hayes, Bernie Sanders was asked if he would tell his supporters to get behind Hillary Clinton if she wins the nomination. He not only refused to say he would, but reiterated his mendacious attacks on her. It is both unprecedented and irresponsible that a candidate would refuse, at this point in a primary, to even entertain the idea of actively facilitating unity behind the candidate in his own party who is likely to win.

During the town hall, a young man asked Bernie, if he fails to win the nomination, if he will “encourage your supporters to vote for Secretary Clinton.”

Bernie replied: “We are not a movement where I can say to you or to anybody else what you should do, because you won’t listen to me—you shouldn’t. You’ll make these decisions yourself. I think if we end up losing—and I hope we do not—if Secretary Clinton wins, it is incumbent upon her to tell millions of people who right now do not believe in establishment politics or establishment economics, who have serious misgivings about a candidate who has received millions of dollars from Wall Street and other special interests— She has gotta go out to you.

He followed that with a list of admonishments to Hillary about what she needs to do and what policies she needs to embrace. Then: “So, the point that I am making is: It is incumbent upon Secretary Clinton to reach out.”

He went on, and eventually, Hayes asked him what Bernie feels is incumbent upon himself, if and when it comes to the point that she wins. At which point, Bernie launched into a criticism of the Republican Party, concluding: “I will do everything in my power to make sure that no Republican gets into the White House in this election.”

Watch the clip:

It is because Bernie has spent 2016 demonizing Hillary, profoundly misrepresenting her positions, and spreading misinformation about whence come her donations that he’s now painted himself into a corner where he gives such incredible, damaging answers to what should be simple questions.

He can’t credibly say he will endorse her, because he’s cast her as emblematic of everything wrong with U.S. politics, and so he evades and deflects—which would be bad enough, but then he launches into a reiteration of the very unfair attacks that put him in that corner in the first place.

At this point, it is clear that Bernie cannot win. And instead of truly doing everything he can to help Hillary—which is the best and only thing he can do to make sure a Republican does not get elected—he doubles down on his attacks on her.

The primary is not the only thing Bernie is losing. If he continues down this path, his own integrity is at risk.