Additional reporting by Katherine Krueger from Hofstra University.

There was a moment Monday night when Hillary Clinton was trying to point out that there is still a lot of hope, a lot of strong institutions, a lot of wonderful people in America’s African-American communities no matter how bleak a picture Trump would like to paint at his rallies.

“There is a lot to we should be proud of and supporting and lifting up,” Clinton said.

Trump didn’t really like what she was saying though. How do we know? He let out a very heavy and audible sigh.

It’s a rudimentary debate rule. As millions of Americans tuned in Monday night to watch Clinton and Trump face off for the first time, as undecided voters were ripe for the convincing, it was key that Trump remain calm and unencumbered by a temperament that has poisoned his debate performances in the past. It was the bare minimum really, but Trump could not resist letting the audience know at every turn what he was thinking as Clinton talked.

Following the debate, the Clinton campaign resisted attributing Trump’s interruptions to gender dynamics. “I don’t know that that behavior is something he only does to women,” Clinton communications director Jennifer Palmieri told reporters at the debate site, in response to a question from TPM. “Viewers saw what they saw, they’ll draw their own decisions about his behavior.”

Early in the debate, Clinton laid out all the reasons Trump may not be releasing his tax returns.

“Maybe he’s not as rich as he says he is,” Clinton projected. “Maybe he’s not as charitable as he claims to be … Maybe he doesn’t want the American people … all of you watching tonight to know that he’s paid nothing in federal tax, because the only years that anybody’s ever seen were a couple of years when he had to turn them over to state authorities when he was trying to get a casino license and they showed he didn’t pay any federal income tax.”

It was the kind of moment where Trump could have just smiled and let it pass. Instead, he took the bait.

After all, Clinton was hitting exactly where she knew Trump wouldn’t be able to remain calm. Clinton was threatening to publicly unravel Trump’s carefully manicured public image as a mega wealthy, gold plated, brilliant businessman. So Trump volunteered what will likely be replayed on campaign ads for weeks to come. He couldn’t resist to interject even if it was to his own demise.

“So … that makes me smart,” Trump said. He didn’t deny not paying taxes there. He laid out why that was such a smart choice.

It was one of several examples of how Trump wading into Clinton’s answers made him like he was falling apart rather than made him look in control. He was spouting off – sometimes almost to say words. Clinton’s style, meanwhile, was to wait, patiently for Trump to finish before returning again to where she was most comfortable, deep in the middle of nuanced policy.

During a moment on trade policy, Trump accused Clinton of hoodwinking the American people on the Trans Pacific Partnership and telling them publicly that she won’t support the final deal even though she initially supported the framework. Clinton tried to explain how the situation had changed, how the specific details of the agreement had caused her to reject the final deal, but before she could get through her answer, Trump interrupted.

“So is it President Obama’s fault? Is it President Obama’s fault?” Trump asked.

“Before you even announced,” Clinton started.

“Secretary, is it President Obama’s fault? Because he is pushing it,” Trump kept going.

Some of Trump’s coldest moments on the stage were moments she forced upon him. As Clinton laid out how she believed Trump had been rooting on the housing crisis, Trump jumped in.

“In fact Donald was one of the people who rooted for housing crisis. He said back in 2006, gee, I hope it does collapse then I can go in and buy some and it did collapse,” Clinton said.

“That is business, by the way,” Trump said.