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 Twitter . The views expressed in this commentary belong solely to the author. View more opinion at CNN.

(CNN) The dream of replacing President Donald Trump has inspired so many Democrats to run for president that they couldn't fit on a single stage. There's no shame in not recognizing all the debaters. Heck, sometimes I fail to recognize my own debaters, but that's never stopped me from doling out grades, as I'm doing now.

A-

Elizabeth Warren

She began the debate seeming a bit nervous and overly anxious in her first answer, which is not unexpected in the biggest moment of her political career. And, while she didn't stray off course, she also didn't answer all the questions directly. However, once she got going, Warren took off. Solid topics for her were jobs, women's health care, and pharmaceutical company profits. And to say "I'm with Bernie" when asked about Medicare for All was so clever, I smiled. Warren also didn't do something... and I liked that the most. While she defended her positions during the back and forth, she mostly stayed above the fray. Thankfully. And she had a great closing statement.

B-

Julian Castro

Castro said it should "piss us all off" when we hear stories of the tragic cost of immigration at the border. I loved his answer -- and he gets bonus points for being the first to directly answer a question.

However, Castro gets dinged because of his constant interrupting. Indeed, it might very well be his fault the debate got out of hand. It was rude and impossible to hear anyone. While sometimes necessary, interrupting should be a last resort, not a weapon of choice . There were times the debate had too much testosterone, and I put the blame largely on Castro.

B-

Cory Booker

Booker was up and down. He had some great answers, such as why health care is needed to succeed in life and why opioid manufacturers must be held responsible for the lives they've ruined. But for every solid answer, he also made mistakes. His attempt to charm viewers by speaking Spanish fell flat and he was a repeat offender of failing to actually answer the question.

C+

Amy Klobuchar

She was good in her closing statement and on the topic of Iran. I liked her answer on guns, when she talked about protecting her uncle's deer stand. And it was smart to point out the three women on stage have been solid on the right to choose. Unfortunately, she forced some answers into places they didn't belong, and appeared awkward more than once with lines like "all foam and no beer," referring to Trump's failed promise to lower drug prices.

C

Bill de Blasio

Nothing great. Nothing terrible. American values and income inequality were solid topics for de Blasio. But he had a couple of odd answers, such as when he forced his "I have a black son" speech into the discussion of guns -- a clear attempt to make sure everyone outside of New York City knew his family.

C-

Jay Inslee

He had two very popular answers about the goodness of unions and badness of Trump. But Inslee produced some odd nonverbal moments with his aggressive eye contact. And during Gabbard's first answer, the camera panned out and I wrote, "Who is that guy on stage smiling like a goober?" Jay Inslee, meet the world.

C-

Tulsi Gabbard

Overall, Gabbard presented herself well. She had a good nonverbal presence and spoke articulately. But, as a lower-polling candidate, she needed to do something more to stand out. While it wasn't a bad showing, it was a rather forgettable one.

F

Beto O'Rourke

I've never written the word "lightweight" as often as I did when analyzing his debate. O'Rourke failed to answer the questions, got beat up by the other candidates, and double-turned himself (a debate term for contradicting his own argument.) He opined that we should have allies with us when we step in to help end atrocities like genocide, and in the same breath mentioned Rwanda. Simply put, in Rwanda, waiting on allies to step in likely contributed to the genocide.

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For O'Rourke, speaking Spanish came across poorly, just as it did for Booker. At one point O'Rourke seemed to have spoken more Spanish than English. Speaking Spanish doesn't make your policies more favorable, or as Julian Castro once said, it doesn't define who a person is or how that person will govern. At least Castro saved his Spanish for the closing.

F

Tim Ryan

Why so serious? Lips pursed, eyes wide open. With his nervous habits and mispronouncing simple words, he was a bit out of his element.

F

John Delaney

Desperation isn't a good look on him.