Everyone was getting along so well that for a while, there didn’t seem much point in debating. They agreed that Donald J. Trump was a bad, corrupt president who deserved to be impeached. They agreed that the middle class is hurting, even though the economy is booming. They made flattering references to one another’s remarks.
But then the topic of “wine caves” came up.
It was about an hour into Thursday night’s Democratic debate. Senator Elizabeth Warren was musing with some self-satisfaction on the topic of how gratifying it is to take selfies with potential voters for free rather than charging “$5,000 or more” when Mayor Pete Buttigieg, next to her onstage and perhaps feeling a bit sensitive, raised his hand to signal that he wanted to say something.
“Can’t help but feel that might have been directed at me,” he said, referring to the fact that he is willing to take donations from corporate donors, while Ms. Warren has pledged not to. “This is our only chance to defeat Donald Trump,” he said. “And we shouldn’t try to do it with one hand tied behind our back.”
It turns out that Ms. Warren was indeed probably directing her remarks to him. “So the mayor just recently had a fund-raiser that was held in a wine cave full of crystals and served $900-a-bottle wine,” she said.
Leaving aside the cave (and the crystals), Mr. Buttigieg responded that he was “literally the only person on this stage who is not a millionaire or a billionaire.”
If Ms. Warren, with a “net worth 100 times mine,” decided to donate to his campaign, he asked rhetorically, neatly casting his regular-person-championing opponent as rich herself, “would that pollute my campaign because it came from a wealthy person?”
No, it would not, he answered.
But as the mayor and the senator continued their bilateral debate over whether candidates should use “purity tests” in fund-raising, Senator Amy Klobuchar, who had been mentally tapping her foot in annoyance elsewhere onstage, interjected.
“I did not come here to listen to this argument,” she declared. “I came here to make a case for progress.” Of course, she added, she herself had never been to a wine cave — although she had visited “the wind cave in South Dakota.”
It was that kind of evening. The Democratic candidates vying for their party’s presidential nomination agreed that their main goal is to defeat Mr. Trump in the general election next November. But to win the nomination, they have to find ways of differentiating themselves from one another without making it look as if they are engaging in an unedifying exercise in the narcissism of small differences.
If any particular candidate was on the menu on Thursday, it was Mr. Buttigieg, who is leading in the Iowa polls and drew some sharp words from Ms. Klobuchar. After he said that his experience on immigration came from real life and not “committees,” she said he had “basically mocked the hundred years of experience on the stage.”
They went back and forth for a while, trading mean remarks about who had experience in what. The exchange that ended badly for him, when she mentioned that although it is true that he was elected mayor of South Bend, Ind., he had lost a statewide race “by 20 points.”
It’s not clear whether Democratic voters unsure of whom to support learned anything new about the candidates at the debate, the sixth since June. (There are at least four more to come in the next two months.)
Ms. Klobuchar mentioned that her grandfather, an iron-ore miner, saved his money in a coffee can. Ms. Warren said that her three brothers had political differences but were united in their resentment of Amazon’s sophisticated tax-avoidance techniques.
Former Vice President Joe Biden looked tan and relaxed and did not do that thing where, when he begins to tell a long, meandering anecdote, you wonder at what point in the day he will arrive at his final verb and wrap up the sentence. He refused to say whether or not he would run for a second term, if he gets elected president in the first place.
Andrew Yang proved once again that he has a good sense of humor about himself — “I know what you’re thinking, America: How am I still on this stage with them?”— and declared, apropos of not much, that “if you get too many men alone and leave us alone for a while, we kind of become morons.”
Tom Steyer mentioned a number of times that he ran a highly successful business, and also demonstrated that he knows what the word “equilibrating” means.
And if anyone was worried about the lingering effects of a recent heart attack on Senator Bernie Sanders, they need not have been: He proved that no candidate can lean forward with more emphatic gusto and declare that he has received more donations than anyone else, at an average amount of $18, than he can.
The debate ended with a left-field question about whether the candidates would like to apologize or give a gift to anyone, and comity was restored.
The men all chose gifts (several picked their own books).
Ms. Warren said she was sorry that she gets “a little worked up” and “a little hot” at times.
“I’d ask for forgiveness anytime any of you get mad at me,” Ms. Klobuchar said.