But following the clash on Monday, conspiracy theorists have set the internet ablaze with rumours that the Democratic nominee may have secretly had help.
Eagle-eyed observers claim to have spotted Clinton, 68, wearing what appears to be an hidden earpiece during the debate.
Footage from the 90-minute discussion at Hofstra University in New York also appears to show the outline of wires and a battery pack under Clinton's jacket.
Catholic Online website asked: "What is it for? Is it so a team can feed her answers? Is it an anti-seizure device? A hearing aid?"
Social media users were also quick to point out that Republican Trump was not wearing a similar device.
Both candidates were clearly fitted with small microphones on their lapels, in addition to the microphones on their lecterns.
Following criticism of his debate performance, Trump claimed he was given a "very bad" microphone and that debate moderator, Lester Holt of NBC News, asked him "very unfair questions".
He told Fox News: "I don't want to believe in conspiracy theories, of course, but it was much lower than hers and it was crackling."
In response, Clinton told reporters on her campaign plane: "Anyone who complains about the microphone is not having a good night."