Vice President Joe Biden’s mood trajectory throughout Thursday night’s debate sharpened the contrast between him and Congressman Paul Ryan, said Matt McGarrity, University of Washington senior lecturer and director of debate.

Ryan stayed calm and measured, McGarrity said, while Biden went from “jovial, to attack, then just angry, and in the end, he’s somber and serious.”

The contrast allowed Biden to challenge — through laughter, then interruptions — almost everything Ryan said in the first half of the debate. Ryan fought back calmly by explaining policies. When Ryan began to interrupt and challenge Biden, McGarrity pointed out, the vice president stopped each time to respond directly.

The result was a marked style difference on top of the stark policy differences expressed during the debate.

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Both candidates were comfortable getting into specifics, said Jeff Philpott, another debate expert from Seattle University.

The debate offered a clearer contrast than last week’s presidential debate because the moderator, ABC’s Martha Raddatz, had a handle on the candidates and their answers, the two local experts said.

Raddatz “stepped in fairly forcefully,” Philpott said. “It’s no easy thing to cut off the vice president of the United States or a member of Congress in mid-sentence, but she was able to do that several times.”

Biden’s laughter — the talk of Twitter — was emphasized by the split-screen format of the debate, Philpot said. An audience member watching live might not have noticed it as much.

“Joe Biden’s gonna be Joe Biden, and he’s gonna say things like ‘malarkey.’ ” Philpott said.

Ryan, he said, seemed comfortable showing off his expertise and came off as a bit of a “policy wonk.”

McGarrity said Biden was challenged less by Raddatz, partly because of the way he responded. When Raddatz challenged Ryan, he engaged her, answering her questions and accepting a follow-up.

“What ended up happening was Ryan, at times, ended up debating Biden and the moderator,” McGarrity said.

Biden, on the other hand, shut down questions from the moderator; he “lectured her,” McGarrity said. “Biden gets very pointed with the moderator when he’s challenged by her.”

And over and over, Biden brought the debate back to trust, McGarrity said, challenging the credibility of Ryan and Mitt Romney by calling them “these guys” and “my friends.”

“That’s not a friendly ‘friend,’ ” he said.

Even when delivered with a smile.

Emily Heffter: 206-464-8246 or