"He's decreasing stress by doing all that movement," Driver said of Trump's behavior on CNN's "New Day" on Monday.
And Driver noted that it was Clinton's own "strategic" decision to range freely around the stage and position herself in front of Trump when she was answering questions that contributed to him appearing to lurk behind her because, Driver noted, he had nowhere to go.
"Hillary is going to his side of the stage and standing in front of him," Driver said. "What's he going to do? Sit down? Go to her seat? So he begins to hover ... She's on his side of the stage. I think this is strategic."
"Did Trump interrupt at all when she was standing in front of him?" Driver added. "Not once."
But Driver also called Trump's movements a "pre-assault indicator."
"At some parts of watching last night, I was really getting nervous because she was in his space," she told CNN's Alisyn Camerota. "He's like a dog who's starting to get anxious and being backed into a corner."
Kellyanne Conway, Trump's campaign manager, called the focus on her boss' body language and movements around the stage a non-story and a "yawn."
But Trump's standing behind Clinton at times Sunday night drew derision from some viewers on social media.
"This looks like a poster for a 1970s horror movie," tweeted New York Times culture writer Dave Itzkoff in response to a photo of Trump standing behind Clinton and frowning.
Senator John McCain was criticized for similar "lurking" in the background on stage during a 2008 presidential debate against Barack Obama when McCain was the GOP nominee.
While the candidates stood at podiums for last month's first debate, the town hall-style debate on Sunday night allowed Trump and Clinton more freedom of movement because the stage was largely empty besides two chairs and two side tables.
Driver also said Clinton "snubbed" Trump at the beginning of the debate by not shaking his hand.
"He looks at her a little longer, about three seconds longer," Driver said. "She turns away first. He was going to shake her hand if she offered first."
But when the candidates did shake hands at the end of the event, Driver said Trump moved to take control.
"When he shook it, he then did that elbow grab," Driver said, "Like, 'I might be cowering down and shaking your hand and giving you power, but I'll talk a little power back with that elbow grab.''"
More mysterious was Trump's sniffing, a behavior the candidate can't seem to get rid of -- it captured the attention of viewers at the first debate, too.
"Last time, he said he didn't have a cold," Driver said. "I said, he probably should say he has a cold, because maybe he's just stressed throughout the whole entire debate, although he was way more prepared this time."