Hi, and welcome to a special post-debate edition of On Politics. I’m Lisa Lerer, your host.

Raise your hand if you knew John Delaney was running for president before last night’s debate.

Oh, Mrs. Delaney, thanks for reading!

The former Maryland congressman may not end up as our next president. But it sure seemed like he was cast in the role of Joe Biden on Tuesday.

In a debate that went deep on substance, beginning with a detailed discussion of health care, Mr. Delaney became a favorite punching bag of Senators Elizabeth Warren and Bernie Sanders. When he questioned the “Medicare for all” proposal, Mr. Sanders shot back: “You’re wrong.”

For Ms. Warren, Mr. Delaney’s criticism led to one of the most memorable lines of the night: “I don’t understand why anybody goes to all the trouble of running for president of the United States just to talk about what we really can’t do and shouldn’t fight for,” she said, firing back at his charges that her ideas were unrealistic.