Donald Trump paced and loomed behind Hillary Clinton at times during Sunday night's second presidential debate - a decision possibly driven by stress during the intensely bitter event, according to body language expert Janine Driver.
Trump's disagreement with running mate Mike Pence over Syria was the top tweeted moment.
Trump was ready to pounce with an ugly counteroffensive.
Clinton showed that fight Sunday night, going after Trump on his crude comments about women, even as he did his best to humiliate her by parading her husband's accusers before her.
"You can say any way you want to say it, but Bill Clinton was abusive to women", he said.
The Atlantic, which endorsed Mrs Clinton last week, suggests that Mr Trump suffered an "implosion" in St Louis on Sunday. The once sacred tradition of a presidential debate - where candidates typically trade barbs over their vision of the country's future instead of personal humiliations - exploded into something quite chilling. The performance likely electrified his fiercely loyal supporters but may have done little to widen his appeal among more moderate swing state voters.
A CNN/ORC survey of debate watchers put her 57-34 up while a YouGov snap poll put her margin of victory closer at 47-42. The poll only represents the views of people who watched the debate and has a slight Democratic advantage compared to CNN polls of all Americans.
"If you look at Bill Clinton, far worse". "Hillary Clinton attacked those same women and attacked them viciously", he added. She didn't take the bait, repeating first lady Michelle Obama's philosophy articulated at the Democratic convention: "When they go low, we go high".
There was even one point when he called Clinton the "devil".
"Nice, one on three" Trump said, claiming that the moderators were biased against him. But he argued that former President Bill Clinton, who was sitting in the front row, had engaged in such acts. The candidates called each other liars and exhibited a depth of hostility that is rare in presidential campaigns.
President Barack Obama's former attorney general, Eric Holder, led the broad condemnation of Trump's threat, as critics painted him as a dictator in the making.
The debate, which featured questions from audience members, was the most tweeted-about debate ever, with more than 17 million tweets, said Twitter spokesman Nick Pacilio.
"He and I haven't spoken, and I disagree", Trump said.
Pence told Fox News that Trump "stepped up" during the debate: "He showed humility".
He suggested he would align himself with some of America's most hostile enemies, including Russian Federation and the government of Syrian President Bashar al-Assad, to fight ISIS. I don't know if it was meant to be a compliment, but I am very proud of my children and they've done a wonderful job and they're wonderful kids'. Does political correctness trump abiding by our laws?