Democrat Hillary Clinton accused Republican Donald Trump of racism, sexism and tax avoidance on Monday, putting him on the defensive during a debate that a snap poll said boosted her White House chances.

Trump, a real estate tycoon making his first run for public office, said Clinton's long years of service represented "bad experience" with few results and said she lacked the stamina to serve as commander-in-chief.

Heading into the debate, staged 43 days from the Nov. 8 election, Clinton was under pressure to perform well after a bout with pneumonia and a drop in opinion polls, but her long days of preparation appeared to pay off in her highly anticipated first 90-minute standoff with Trump.