Does Donald Trump have a cold? He began Monday night's debate at Hofstra University occasionally sniffling, which appeared to distract many people following along on social media.
It wasn't clear if Trump had a cold, and Trump's sniffles only made occasional reappearances. When Hillary Clinton had pneumonia about two weeks ago, it became a major question mark over her own campaign.
When video showed her appearing to stumble at a 9/11 memorial event in New York, it sparked a wave of speculation on whether she was fit enough to continue running or serve as president. (Her doctors said she was, and she returned to the trail.)
Trump's campaign did appear to make light of her absence from the campaign trail in a statement after she began campaigning: "We are pleased to disclose all of the test results which show that Mr. Trump is in excellent health, and has the stamina to endure — uninterrupted — the rigors of a punishing and unprecedented presidential campaign and, more importantly, the singularly demanding job of president of the United States."
Still, the sniffles did not go unnoticed.
Taxes vs. Emails
The emails deleted from Clinton's private server and Donald Trump's audited tax returns are the big unknowns of this campaign.
Trump offered to put his taxes out there when Clinton releases all 33,000 of those emails he says were deleted.
Clinton said, "I made a mistake using a private email" server.
Trump interjected, "That's for sure" and Clinton shot back, "I take responsibility for that."
Trump said Clinton forced support staff and technology officials to take the Fifth Amendment, rather than incriminating themselves in the subsequent investigation over her emails.
Trump said voters wouldn't be blown away by his tax returns because "you don't learn that much from taxes."
But Clinton speculated there would be a lot to learn there: "Maybe he's not as rich as he says he is" or "maybe he's not as charitable as he claims to be."
When Clinton suggested he hasn't paid federal income taxes for years, Trump pointed out, "that makes me smart."
Moderator Lester Holt asked Trump about his longtime advocacy of the so-called birther movement, in which Trump and others pressed for the release of President Barack Obama's birth certificate.
They wanted proof Obama was born in Hawaii — he was — and not in Kenya, where he has family. A replica of the Hawaiian birth certificate was eventually produced, but Trump only agreed this week that Obama was born in the United States, then didn't take questions
When asked Monday why he continuously pushed the birther theory, Trump said, "Nobody was pressing it, nobody was caring much about it... I was the one who got him to produce the birth certificate."
Clinton replied by calling the birther claim "a very hurtful" lie: "He tried to put the whole racist birther lie to bed. But it can't be dismissed that easily."
Temperament and judgment have become major issues in the 2016 election, fought between two candidates with styles that clash between hot emotion and cold logic.
"I have a much better temperament than her," Trump said, calling the Clinton campaign's long-standing attempts to attack his temperament a classic Madison Avenue line.
Clinton replied by citing Trump being supposedly "provoked by a tweet" — he said he'd never allow American service members to be mocked, as he's asserted a group of sailors were before being taken into custody by Iran.
"That is not the right temperament to be commander-in-chief," she said, arguing a president should show reserve.
Trump countered by saying Clinton's assertions were "all lies."
The Associated Press contributed to this report.