The first US presidential debate, a clash of titans Monday between Democratic candidate Hillary Clinton and Republican Donald Trump, is one of the high points of the campaign, six weeks from the November 8 elections.
This first of three nationally televised debates will give the candidates a chance to introduce themselves -- or re-introduce themselves -- to skeptical American voters who will be watching closely for the slightest misstep, awkward gesture or fatal altercation.
It could shatter records for a television audience, with an estimated 90 million people expected to tune in, drawn by the high contrast between candidates and an extremely tight race.
Monday at 9:00 pm (0100 GMT), at Hofstra University in the city of Hempstead on Long Island, an hour's drive from New York. Hofstra is no newcomer to presidential debates, having hosted them in 2008 and 2012.
Ninety minutes, in six 15-minute segments with no commercial interruptions. Questions will focus on three broad themes: "America's Direction," "Achieving Prosperity" and "Securing America."
The two candidates will be alone on the stage, each standing behind a lectern.
The moderator will open each segment with a question. Each candidate will have two minutes to respond; each will then be allowed to reply to the other's response. The moderator will use the remaining time for follow-up questions.
Each broad theme will be discussed for 30 minutes.
Lester Holt, 57, the respected anchor of NBC's evening news program, the country's most widely watched. He moderated one of the Democratic primary debates in January.
The bar is higher for the Democratic candidate, given her experience and detailed knowledge of the issues. Clinton will have to show that she is presidential but also honest (66 percent of Americans do not think so), while proving that she has fully recovered from her recent bout of pneumonia. Clinton is not particularly well-liked, and anything she can do to create an emotional bond with voters could boost her cause.
Trump needs to convince voters that he has what it takes to be president, that he has at least an adequate familiarity with the issues and can make it through a high-pressure debate against a single opponent without losing his self-control. He also needs to reassure Republicans that although he is in many ways an outsider, he would serve as a Republican president.
The current record for a televised presidential debate is 80.6 million viewers, set by the 1980 encounter between the Democratic incumbent, Jimmy Carter, and his Republican challenger, former California governor Ronald Reagan. Many analysts expect that to be broken on Monday.
Gary Johnson, the Libertarian candidate, and Jill Stein, the Green Party nominee, were not invited to the debate. They did not reach the threshold, set by the Commission on Presidential Debates, of an average 15 percent support based on five national opinion polls.
Johnson's support is currently at 7.2 percent and Stein's at 2.3 percent.