After Bloomberg charged that Russians were interfering in the primary on Sanders’s behalf as a way of handing Trump his weakest opponent, Buttigieg chimed in: “They want chaos, and chaos is what is coming our way. I mean, look, if you think the last four years has been chaotic, divisive, toxic, exhausting, imagine spending the better part of 2020 with Bernie Sanders vs. Donald Trump. Think about what that will be like for this country.”

He later told Sanders that his nomination would jeopardize Democrats’ hard-won control of the House, saying that the scores of Democrats whose victories in 2018 gave the party its majority “are not running on your platform. They are running away from your platform as fast as they possibly can.”

Sanders, red-faced, shook his head. He did so much of that on Tuesday night it was as if he were a pioneer in neck aerobics.

But he also kept his cool and stood his ground, so that a night devoted in large part to wounding him probably left him with little more than a nick or two. He was able to say, correctly, that he beats Trump in polls that posit a hypothetical matchup of the two. He was able to cite, accurately, his impressive favorability ratings.

He was also able to step back during stretches of the debate when the ugliness didn’t focus on him — when the generally foul atmosphere pitted Biden against Steyer or Warren against Bloomberg, or Klobuchar against Biden.

Nobody really looked good, and that’s another big part of what spooked me. I was watching a political party devour itself. It was all so unpleasant — and so unflattering — that candidates took to commenting on how unpleasant and unflattering it was.

“I guess the only way you do this is to jump in and speak twice as long as you should,” Biden groused, as he delivered yet another debate performance in which he was obsessed with the clock, the rules and whether he should follow them when others didn’t.