Editor’s Note: Todd Graham is the director of debate at Southern Illinois University. His debate teams have won five national championships and he has been recognized three times as the national debate coach of the year. Follow him on Facebook and Twitter. The views expressed in this commentary belong solely to the author. View more opinion at CNN.

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In the final Democratic primary debate before voting begins in Iowa, two candidates separated themselves from the field. Unfortunately for one of them, they landed at the bottom of the pack.

A

Pete Buttigieg

Buttigieg was in a great spot to have his strongest debate yet. He focused the Midwestern setting into a theme: progressive pragmatism at its best. Buttigieg’s content and presentation easily made him the best debater Tuesday night.

Todd Graham

He saved his finest arguments for the most important topics. In competitive debate circles, we call those topics “voting issues,” and that’s where Buttigieg was sweet. On trade deals, Buttigieg reminded the Midwestern voters that the pie was not getting to the people where he lived. He was clearer and more focused with his health care plan than he has been in previous debates, spelling out two moves — negotiating prescription drug prices and rolling back President Trump’s tax cuts. To close the theme, Buttigieg, the former two-term mayor of South Bend, Indiana, reminded us that the burden of spending taxpayer dollars always requires a choice and he chose wisely by arguing against free college for the wealthy.

Finally, Buttigieg crushed it in a flurry of fantastic arguments toward the end, acing the final question about electability. Buttigieg confidently stated that Trump can’t stand next to a war vet and explain his bone spurs excuse — and that Trump and Republicans can’t use Christianity to recruit voters because Buttigieg’s faith is also strong.

B+

Tom Steyer

I was hoping that Steyer would not attempt his usual never-ending staring contest with the cameras. To my surprise, he did not, and it did him wonders because while I appreciated Steyer’s concise answers, I also liked his personality. Steyer smartly and overtly agreed with several people onstage, proving one of my best debating tips: You don’t have to disagree on every point to win an argument. Agreement often improves your likeability and credibility, which can come in handy later in the debate. Indeed, Steyer happily rode those coattails when he affirmed the positions of some of the other candidates when they were having their best moments.

Steyer’s strength was in his passionate fighting — I noticed it time and again. I particularly liked his improved answer on why he was the right messenger for climate activism. Steyer said yes, and that he’s been winning fights for climate during the last 12 years. Steyer reminded the audience that he’s not only been fighting for climate, but he’s led the fight to impeach Trump.

Finally, Steyer pivoted and aggressively predicted that he’d beat Trump on the Republican leader’s perceived strength: The economy. Given Steyer’s experience in business, I found his argument persuasive.

B+

Elizabeth Warren

Warren was steadfast in both her verbal tone and argument quality when making the case that we need to bring combat troops home. She cleverly explained how “one general after another” would brief her that “we’ve just turned the corner,” yet nothing would change. The Massachusetts senator advocated a troop withdrawal better in the debate than I’d previously heard, and she finished her position by stating, “It’s not enough to say some day we’re going to get out.”

Warren was on point in support of why women can win elections when she wryly stated that the only people on stage to never lose an election were the two women. Plus, I thought she swatted back the question about supporting government run drug manufacturing and turned it in her favor by using an argument straight out of the conservative playbook: She argued that by allowing more generic drugs to be sold, the markets would be more competitive thereby driving prices down.

Unfortunately, her worst answer was on the final question. She was asked if she would scare away swing voters. In response, Warren focused her answer on everyone but herself, mentioning her brothers and uniting the country. This was the moment when Warren should have boldly sold herself as a winner and she missed the opportunity.

C+

Joe Biden

I’ll say this for the former vice president. He stuck to his theme of “manners maketh man.” I think Biden has realized that his debating skills have diminished somewhat from previous campaigns. Instead of trying to win each point, Biden’s focus seemed to be on his personability. This singular theme might very well be his best argument for why he should win the nomination and he played his “anti-Trump” card effectively.

When Wolf Blitzer asked about running against Trump “after what he’s said about your family,” Biden was sincere. He summarized, “I can’t hold a grudge. I have to be able to not only fight, but also heal.” And in the last question of the debate, Biden’s theme was that “character” will be on the ballot.

But Biden’s weakness was still evident in many of his answers. They weren’t crisp. His language was often imprecise or unclear, and he still never seems to get through an answer smoothly. Biden wasn’t terrible. But he wasn’t impressive either.

C+

Bernie Sanders

Oh, Bernie.

One of the funniest ‘presidential debate’ moments just repeated itself.

Sen. Sanders made a major unforced error and reminded us that math is, well, hard. Sanders attempted to correct Warren’s claim that she was the only person onstage in the last 30 years to beat an incumbent. After all, the Vermont senator bragged, he’d only beaten one in 1990. Then, everyone awkwardly waited while the two senators, one who graduated from the University of Chicago, and the other who taught at Harvard, tried to compute the difference between 1990 and 2020. Both seemed puzzled and the bit went on longer than an Abbott and Costello routine.

However, Sanders was persuasive on many other issues. When he was asked about people losing their jobs in the insurance industry in Des Moines and elsewhere because of his health care plan, Sanders was direct and specific. His plan would provide a transition fund of “up to five years income and health care and job training for those people.” And he said twice in the debate that “every other major country on earth” guarantees health care, so his ideas seemed not extreme but the norm.

F

Amy Klobuchar

Sen. Klobuchar had a moment of forgetfulness. She couldn’t remember the name of the Kansas governor, and her stalling technique — awkwardly saying “and her name is …” before remembering it — only dug her into a deeper hole. While it wasn’t an absolute disaster, it was still unfortunate.

It was her other constant error that ruined her performance. One of my primary rules for any debate: The timer is your enemy.

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    The Minnesota senator continually spoke over her allotted time, and last night the moderators called her out on it. Unfortunately for Klobuchar, it appeared she was saving the best part of her answers for a big finish. But she never got the chance because she was cut off by the moderators or there was cross talk making it impossible to hear her. By the time the debate concluded, Klobuchar seemed a shell of her usual confident self. You could hear it when she stumbled over words and see it in her nonverbal expressions. The end couldn’t have come any faster for Klobuchar. If it’s her last debate, it was an awful way to finish.