Todd Graham is the director of debate at Southern Illinois University. His teams have won five national championships and advanced to the "final-four" of a national championship tournament nine consecutive years. He's been recognized three times as the national debate coach of the year. The opinions expressed in this commentary are his.

(CNN) Last night, Tim Kaine and Mike Pence took up their most public roles yet as surrogates for their leaders in the vice presidential debate.

Knowing this, they each had three roles:

First, defend the top of your ticket. Second, attack the top of the other ticket. Finally, prove you are capable of being president. Once I got past the interruptions, here's what I heard.

Defend the top of your ticket

Tim Kaine: B+

I thought the email attacks hit home , especially when Pence hammered away at the fact that it was dangerous for American security. Kaine's answer was only that it was not "criminal." OK, but that's not really the point. He defended everything else pretty well, from the Clinton Foundation to the Iran deal. He was ready with the fact that Clinton apologized for the " basket of deplorables" line . Indeed, Kaine used the old backward-step-pivot-forward debating technique by turning this into an indictment of Trump's lack of apologies for anything.

Mike Pence: D-

Pence was clearly uncomfortable. This reminds me of so many debates my teams have had. In every debate, we are a team of two members. When one of my debaters is young or inexperienced, they make a lot of mistakes that the older member tries to overcome in the final speech.

That's precisely what happened here. Trump, in his stump speeches and the first presidential debate, was like my younger, inexperienced debaters, just saying things without thinking about the ramifications. Pence was like my seasoned veterans, trying to gloss over, re-explain, and even change the direction of the answers given by their partner.

JUST WATCHED What Mike Pence thinks vs. What Donald Trump says Replay More Videos ... MUST WATCH What Mike Pence thinks vs. What Donald Trump says 02:14

Unfortunately, it usually leads to double-turns. (A double-turn is when a team directly contradicts something they've said earlier.)

Since Pence didn't want to contradict Trump, his only other option was silence. And it was painful to watch him getting hammered again and again by Kaine. Kaine even asked, "How can you defend that?" multiple times on these subjects:

-- The Trump insult about John McCain and prisoners of war

-- The Trump insult about the Indiana judge not being qualified because of his heritage

-- The Trump claim that more countries getting nukes is a good thing

-- The Trump argument questioning NATO and alliances

-- Trump's (and Pence's) comments about how Vladimir Putin is a strong leader

-- Trump's taxes

-- Trump's line that Mexico is sending criminals, drug dealers and rapists across the border

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In debate terms, Pence got "spread out of the debate." There were too many attacks and he had too few answers for them. Plus, his heart wasn't there. Pence defended his own positions just fine; defending Trump was another thing.

Multiple times, I thought he just gave up. He seemed frustrated, saying "did you work on that for a long time?" and "don't put words in my mouth." Unfortunately, it was Trump who put the words there, and Trump's own words were Pence's undoing.

Attack the top of the other ticket

Tim Kaine: A+

Mike Pence: B+

Kaine found the sweetest fruit to be the lowest hanging.

Finally, immigration and deportation was debated. These were the attacks Pence at least tried to defend. The rest he tried to brush off and ignore, which left Kaine free to attack Trump at will.

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As for Pence, he had his own good moments with criticisms of Clinton. He hammered the emails, the server, and our security several times. He was also pretty effective with his "Clinton reset Russia" argument (but honestly, I wish he'd spent 30 seconds explaining the term "reset Russia" and what, exactly, that meant).

Pence was also prepped to debate the lack of action by Obama and Clinton led to the creation of ISIS. Finally, he got to use the "basket of deplorables" line against Clinton and how she'd insulted too many people. All these were reasonable criticisms of Clinton that scored to some extent.

But in an emergency...

Tim Kaine: A-

Mike Pence: A-

Both candidates demonstrated the experience necessary to take over the role of president if needed. They both had detailed answers on questions ranging from the economy to their religious beliefs and abortion. Based on this debate only, yes, I think they are both qualified to be president. Not perfect, but qualified.

Overall grade

Tim Kaine: B (I deducted a letter grade for excessive interrupting)

Mike Pence: C (Defending Trump isn't his forte)