For months now, Democrat Hillary Clinton and Republican Donald Trump have been sparring at each other from afar. On Monday they'll do it face to face, on a stage at Hofstra University on Long Island in New York.
Debates have been a mainstay of presidential campaigns, it seems forever. But that's not quite the case: The first general election debate didn't occur until 1960, in a Chicago TV studio, between Vice President Richard M. Nixon and Senator John F. Kennedy.
Monday's debate between Clinton and Trump will take place on the 56th anniversary of that first debate.
NBC's Lester Holt will moderate. And there's already been a lot of talk about how he'll go about it, especially regarding whether he should be fact-checking the candidates' answers. The co-chairman of the Commission on Presidential Debates, Republican Frank Fahrenkopf, doesn't think so.
Fahrenkopf says if "Candidate A" says something that is wrong or inconsistent with what they've done or said in the past, "it's not the moderators job to say, 'hey, Candidate A, that's not what you said last week.' That's for Candidate B to do."
Bob Schieffer agrees. The former CBS News anchor moderated three presidential debates. At a panel discussion at the University of Notre Dame recently, he said in his view "the role of the moderator is to be the referee, it's not to be a judge." Schieffer says the moderator's role is to conduct a discussion that gives viewers "a fuller understanding of what these people think on various subjects."
Monday's 90-minute debate will be divided into three parts: America's Direction, Achieving Prosperity, and Securing America.
The candidates will stand at podiums. In at least one previous debate, that was a sticking point. In 1988, there was a rather big height disparity between democrat Michael Dukakis and the much taller George H.W. Bush.
Fahrenkopf says the commission solved the problem by building what he called "a pitcher's mound" behind the Dukakis podium. That way, Fahrenkopf says, when Dukakis stood at the podium, "the top of podium hit him at the same level as it hit Bush."
Sometimes debates are campaign turning points. In 1984, Ronald Reagan's age — at 73, he was the country's oldest president — became an issue after he seemed unfocused during that campaign's first debate.
In the second, though, he nimbly turned a question about his age into an advantage — and a jab at his Democratic challenger, Walter Mondale — by quipping, "I will not make age an issue of this campaign. I am not going to exploit, for political purposes, my opponent's youth and inexperience."
Debates can also provide lasting images that can reinforce perceptions of a candidate. In 1992, George H.W. Bush was criticized after he glanced at his watch during a debate, as though he had somewhere better to be. In 2000, Democrat Al Gore's theatrical sighs while listening to Republican George W. Bush were mocked.
And four years ago, Republican Mitt Romney awkwardly responded to a question about hiring more women in government, saying that as governor of Massachusetts he went to a number of women's groups and said, "Can you help us find folks and they brought us whole binders full of women."
Will there be any such memorable moments on Monday? We'll see. It's expected to be one of most widely watched debates ever on TV, with millions more streaming it on their portable devices.