Dow futures turned positive, trading more than 100 points higher as Hillary Clinton appeared to gain momentum over Donald Trump amid the debate.
"No big policy statements but she is on her game and he is on the back foot. Market has her priced in to win," said Peter Coleman, head trader at Convergex.
"I think traders were looking for a surprise from Trump. Now he is on the offensive," he said.
Dow futures traded about 60 points higher as of 9:56 p.m. ET, while S&P 500 futures were about 7 points higher and Nasdaq 100 futures about 14 points higher.
Ahead of the debate, futures for the three indexes were lower, with Dow futures about 30 points lower. The Dow Jones industrial average closed more than 150 points lower Monday.