Tuesday's US presidential debate, a combat of titans pitting the Democrat Hillary Clinton against the Republican Donald Trump, is sure to be a major moment in the campaign, with just six weeks left before the 8 November election.
This first of three 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.
The debate could break all records for a US political audience, given the sharply contrasting personalities — and positions — of Trump and Clinton.
Time and place
Monday at 6:30 am IST (0100 GMT), at Hofstra University in the city of Hempstead on Long Island, an hour's drive from New York. Hofstra is no newcomer presidential debates, having hosted them in 2008 and 2012.
Length and format
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 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 Democrats' primary debates in January.
The stakes for Clinton
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 (55 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 would boost her cause.
"We typically don't tune in to our televised debates to see who's the smartest of the two candidates and which one has the most facts and figures and policy information that they're spewing for 90 minutes," Mitchell McKinney, professor of political communication at the University of Missouri, told AFP.
McKinney, a specialist in political debates, said television viewers favor candidates who manage to communicate their vision in a few simple, compelling and memorable phrases.
Clinton, with her diligent and detailed mastery of the issues, will have to avoid falling into the trap of giving overly technical and exhaustive responses to the moderator's questions.
"You need to generate a more emotional connection with voters if you're going to prevail," said communications consultant Carmine Gallo.
In the words of Obama, who was asked what debate advice he would offer his former secretary of state: "Be yourself and explain what motivates you."
That has been a constant challenge for Clinton, the least loved of Democratic presidential candidates in years, according to polls.
Clinton herself acknowledges that she cannot match the charisma of her husband, Bill Clinton, or of Obama. More than half of Americans say they are not sure they can trust her.
During her first run for the presidency, in 2008, Clinton presented herself as a tough, Thatcher-style "iron lady." This time, she stresses her role as a pioneer for women's rights and polishes her image as a grandmother, in an effort to seem more likable and accessible.
But it will not be easy for her to wipe away, in a 90-minute debate, an image forged in public opinion over a quarter-century.
Her strength may lie in her ability to counter any attack with an effective verbal comeback.
"What are those one, two or three key messages that they want people to share on Twitter and social media?" Gallo asked. "Listen for the sentence or two that she repeats several times in the conversation."
The stakes for Trump
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.
"Trump connects to his voters on a deeply emotional level, and that can be quite difficult for an opposing candidate to match, because emotion often trumps data," Gallo said.
In this area, the wealthy populist, former host of a successful television program, enjoys a clear advantage.
No candidate in this campaign — with the possible exception of Democratic senator Bernie Sanders — has matched Trump's ability to electrify crowds of thousands.
But Trump did not hold the upper hand in every one of the 12 Republican primary debates. He often stood aside to let the other candidates rip into one another.
In the later debates, when only a few of his adversaries remained, he often resorted to disruptive tactics, using scathing phrases or demeaning nicknames to savage his opponents.
"Unlike the primary debates, where there were multiple candidates on the stage and therefore we heard from Trump periodically, in a 90-minute debate where he's going to have half the time, he can't fill all of this time with one-liners, with self-praise, with the glib attacks — that will wear thin," McKinney said.
"He will have more opportunities to provide substance. When that time comes, will he have the substance? We will be watching to see."
The concern of the Clinton team is that the moderator, Holt, will toss simpler "softball" questions in Trump's direction while pressing Clinton with a much more challenging interrogation.
Either way, these exchanges are sure to be intensively analyzed afterward as part of the continuing debate... on the debate.
Gary Johnson, the Libertarian candidate, and Jill Stein, the Greens Party nominee, were not invited to the debate. They did not reach the threshold, set by the Commission on Presidential Debates (CPD), of 15 percent support in five national opinion polls.
Johnson's support is currently at 8.9 percent and Stein's at 2.9 percent, according to an average of recent surveys.
A new audience record?
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.