The attacks turned personal as Republican Donald Trump accused his rival Hillary Clinton of not having the right temperament to be president. Mrs Clinton baited Mr Trump by pointing out that he refuses to release his tax returns.
Trump hit Clinton on trade and her political record – issues that have helped him draw level in recent polls and may yet dominate the election – but the property tycoon appeared thin-skinned and under-prepared as he sniffled his way through the debate.
Questions of stamina and temperament were levelled instead at Trump as he appeared to lose concentration during the uninterrupted appearance – his first one-on-one appearance on a political debate stage.
Some of his responses seemed little more than free-associative non-sequiturs. “I have a son who’s 10, he’s so good with computers,” said Trump when asked about US cybersecurity weaknesses.
She also accused him of “stiffing thousands” of contractors by declaring bankruptcy as a businessman. And in a powerful closing argument she highlighted Trump’s record of sexism, noted that he had called women pigs and slobs and, in one case, called a beauty contest Miss Housekeeping “because she was Latina”.
In turn, Trump attacked Clinton’s suitability as president in blunt terms. “She doesn’t have the look and she doesn’t have the stamina,” he said. “I’ve been all over the place. You decided to stay home,” he added.