Analysis by Chris Cillizza, CNN Editor-at-large | CNN

A dozen (!) Democratic presidential candidates took the stage in Ohio for the fourth debate of the 2020 election, the largest field ever to participate in a single debate.

I watched, took notes, tweeted and picked some of the best -- and the worst -- of the night. My winners and losers are below.

WINNERS

* Pete Buttigieg: The South Bend mayor had one clear goal in the debate: Hit Elizabeth Warren on her support for "Medicare for All," and make sure Democratic voters knew he had an alternate plan that would not eliminate the private health insurance market. Mission accomplished. And remember: The polling I've seen makes clear that voters prefer a plan that preserves the right to choose a private insurance plan than one that gets ride of the private market in favor of a government-run plan. Buttigieg didn't stop there. His response to Rep. Tulsi Gabbard's call to end "endless wars" was powerful, leaning heavily on his own military service. He slammed former Rep. Beto O'Rourke on gun control, with one of the lines of the night: "I don't need lessons from you in courage, political or personal." From beginning to end, Buttigieg was a dominant and commanding force. Yes, some will say he was "mean." But debates -- and primaries! -- are about drawing contrasts, and that is what Buttigieg did. And did very well.

* Andrew Yang: If I told you even three months ago that there would be a time in mid-October in which there was an extended conversation in a Democratic debate about the dangers of automation, you would have laughed at me. And yet, there we were on Tuesday night -- a full debate within the debate, about Yang's pet issue. It's a testament to Yang's remarkable rise in this race -- second only to Buttigieg's -- and to the fact that he is already having a significant impact on the conversation within the Democratic Party. Plus, that "MATH" pin was straight fire.

* Amy Klobuchar: At the moment, the Minnesota senator hasn't qualified for the next debate in November. Knowing that, Tuesday night was her last best chance to make a real move. And to her immense credit, she went for it. Knowing that Warren is now the front-runner (more on that below), Klobuchar went right after her. "Your idea is not the only idea," Klobuchar told Warren at one point. At another, she tried to make clear that Warren had no monopoly on "bold" ideas. At yet another, she accused Warren of "making Republican talking points right now." I'm not sure it changes anything in her polling. But she deserves credit for taking her best shot(s).

* Bernie Sanders: If you were watching the debate to see how Sanders fared in the wake of his recent heart attack, well, he was the same old Bernie: Irascible, impatient, sneaky funny and entirely unapologetic about his liberal solutions to the problems facing the country. In a moment indicative of Sanders' night, he was asked a question about his health, muttered something like "I'm fine" and then pivoted to talk policy. Also, it doesn't hurt that the news that New York Rep. Alexandria Ocasio-Cortez would be endorsing him broke during the debate.

LOSERS

* Elizabeth Warren: Welcome to being the front-runner! Although polling suggests that Warren and Joe Biden are co-front-runners, it was crystal clear Tuesday night that the other 11 candidates on stage viewed the Massachusetts senator as the top dog. Which, in theory, is a good thing for her! But in practice, it didn't work out well. Buttigieg started things off by attacking her on Medicare for All -- and Warren was unable to provide a clear answer on a) whether she would raise taxes on middle-class Americans and b) if not, how would she find the money to pay for the plan. The hits kept coming. By my count, at least seven candidates attacked Warren at some point in the night -- and while she remains a very able debater, she was unable to parry all of those attacks effectively. Also, Warren saying that she'd like to see the US military presence gone entirely from the Middle East is going to come back to haunt her.

* Joe Biden: I wrote today that Biden needed a performance that wasn't just "good for Biden" but good by any measure. He came close-ish but, to my mind, didn't do enough. (Worth noting: I thought this was Biden's best debate performance; his answer on his age and health was probably his best answer of the debate season.) His answer on his son, Hunter, and Ukraine was meh: "My son's statement speaks for itself" was the best he could do, knowing that question had to be coming? And maybe it will play differently on replay, but Biden's shout-y "I got you votes" move on Warren felt not so good in the moment. I get the argument that Biden didn't take any big punches in this debate and stayed off the canvas. But ask yourself: is that the right bar for a former vice president and front-runner in this race from the jump?

* Kamala Harris: Nothing Harris did on Tuesday night will change her trajectory -- downward in this race. Her "Dude gotta go" line about Trump fell flat, as if the audience had sort of been there and done that. Harris' attempt to force Warren to agree with her that Donald Trump's Twitter account should be suspended felt small and not terribly effective. Harris has simply not been able to recapture the magic she had in that first debate of this election; Tuesday night was another swing and miss.

* Tom Steyer: When the most interesting thing about you in the debate is that you wore a plaid Christmas tie, you didn't have a good debate.