She was referring to Tom Steyer, who was making his Democratic-debate debut.

Warren said that she had nothing against billionaires per se and wasn’t in the demonization business. She was in the justice business. And with her final remarks, she sought to underscore that with praise for a prominent Republican ally of the first President Bush. She also noted that two of her three brothers were Republicans and that she loved them very much.

The third reason I appreciated this debate is because it so perfectly underscored the most prominent candidates’ rationales for running and arguments for themselves. Apart from that odd exchange with Warren, Biden had a decent night, partly because he was given, and took advantage of, several opportunities to stress that he was more prepared for the presidency than anyone else and that the post-Trump era called for someone who wouldn’t have a steep learning curve. The repair work must begin immediately.

Buttigieg made clear that what he offers, at the tender age of 37, is a truly fresh perspective. He had a superb night, because he embraced a role as Warren’s inquisitor and because several supremely eloquent remarks about foreign policy — in particular, about Trump’s withdrawal of American troops from Syria — allowed him to project a command and maturity that some voters needed to see to consider him seriously.

Cory Booker quintupled down on his pitch as the candidate of love — and was so expansively loving to several of the other Democrats, including Kamala Harris and Biden, that I found myself wondering if this debate was a bid to salvage a flagging campaign or the beginning of an audition to be the eventual nominee’s running mate. As for Harris, she had strong moments, but they were neither strong nor frequent enough to alter her fortunes.

This was the most crowded televised presidential debate ever, with 12 candidates, so I’d need the column equivalent of “War and Peace” to appraise all of them. Still I’d feel remiss if I didn’t note that Sanders, who recently suffered a heart attack, seemed no less vigorous than he had before.

But Warren, not Sanders, was carrying the progressive mantle on Tuesday night, when her less liberal competitors sought with a new assertiveness to trip her up. I don’t think that they quite succeeded.

Warren exits this latest debate as strong as she entered it. And those of us who watched it understand her — the calculations behind her positioning, the potential miscalculations of her monumentally expensive plans and the profound conviction she summons — better than ever before. That’s no small payoff for three long hours.

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