The two US presidential candidates have clashed over jobs, terrorism and race in a bitter television debate.
The attacks turned personal as Republican Donald Trump accused his rival Hillary Clinton of not having the right temperament to be president.
Meanwhile, Mrs Clinton baited Mr Trump by pointing out that he refuses to release his tax returns.
The New York showdown could be the most watched debate in TV history, with up to 100 million viewers.
Hours before the programme, polls suggested the candidates were locked in a dead heat, adding to the tension between the rivals on stage throughout the debate.
“I have a feeling that by the end of this evening, I’m going to be blamed for everything that’s ever happened,” Mrs Clinton quipped when prompted to respond after one of Mr Trump’s attacks.
“Why not?” Mr Trump interrupted.
“Yeah, why not,” she answered. “You know, just join the debate by saying more crazy things.”