This is it - the final stretch of the US presidential race.

After a campaign that started in March 2015, when the first candidates put their names forward, we're now just six weeks away from the election.

The first of three presidential debates takes place on Monday night - and there is plenty to look out for as the candidates edge ever closer to each other in the polls.

What's at stake?

By Anthony Zurcher, BBC North America reporter:

The debates are the last, best chance for Donald Trump and Hillary Clinton to make their case to the nation.

Neither candidate will be able to command the attention of the American public the way they will in the three upcoming presidential debates. And no debate will have as large an audience, or do as much to shape public perceptions of the candidates, as this first one.

There's a good chance Monday night's affair will break the record of 80 million Americans who watched incumbent Jimmy Carter face-off against Ronald Reagan in 1980.

In an election cycle that's measured in months and even years, this debate gives Americans a real, unscripted opportunity to see how the would-be presidents might handle the intense stresses of the Oval Office. It's the mother of all job interviews.

The format

Media playback is unsupported on your device Media caption How do you debate Donald Trump?

There'll be six segments of about 15 minutes, each on a different topic. The moderator is NBC anchor Lester Holt; the venue is Hofstra University on Long Island, New York; the start time is 21:00 local time (01:00 GMT).

At the start of each segment, the two candidates will have two minutes each to respond, then they will respond to each other.

Three of the topics already announced, and selected by Holt, are: America's Direction; Achieving Prosperity and Securing America, which risk sounding more like the slogans of banks than debate topics.

Three more questions related to events in the news this week will also be scheduled.

(There are no breaks during the 90 minutes, so a strategic pre-debate bathroom visit is advised).

Debate bingo

When you hear the following terms, cross them off and see how quickly you can fill in a row of three in any direction...

What they need to do

by BBC North America editor Jon Sopel

Someone once gave me great career advice on handling job interviews - think in terms of what is the question you have to answer. The interview panel will know your work, and have your CV - but what is the one area where they will need convincing?

And so it is in Monday's debate, except the selection board is a little bigger -the 200+ million US electorate.

For two candidates who are uniquely unpopular, they both have their own mountains to climb. Hillary Clinton's CV goes on for pages, so she doesn't need to unveil 15-point plans. Voters know she's got that. But trustworthiness? That's been more difficult. Try to be straightforward, don't be overly defensive or legalistic.

And Donald Trump? Well the CV is much more scant - so he needs to show that there is substance. We know what he wants to do - build a wall, bring back jobs, crush IS, renegotiate trade deals - but how is he going to do it? At the moment we have no idea.

Second time lucky for Clinton?

How Donald Trump had the last laugh

What they need to avoid

"Clinton has to be careful," Mr Trump's ghostwriter Tony Schwartz, who has advised her campaign, told the New York Times. "She could get everything right and still potentially lose the debates if she comes off as too condescending, too much of a know-it-all."

Mr Trump, on the other hand, needs to avoid rising to any bait dangled by his rival. His campaign has indicated we will see a calm, composed Mr Trump in the debates.

What you should look out for

On one hand, there's Mrs Clinton, who has undergone intensive preparation for the debates.

On the other, there's Mr Trump, the former TV personality whose performances in the Republican primary debates helped propel him to the party's candidacy.

The Clinton campaign has been forensically poring over footage of Mr Trump's performances in those debates.

What they concluded, the New York Times reported last month, was that he could be baited into making mistakes, and could respond with unflattering aggression if questions are raised about his intelligence, net worth and business acumen in particular.

Media playback is unsupported on your device Media caption Decoding Trump's top five hand gestures

Mr Trump hasn't employed a stand-in for Mrs Clinton to rehearse the debates, and has reportedly not paid too much attention to briefing notes on policy.

Instead, reports say, he has relied heavily on advisers Rudy Giuliani (the former New York mayor) and Roger Ailes (the former Fox News chief) - all while playing golf and sharing hot dogs with them.

Last week, his campaign also sent a questionnaire to his supporters, asking them for their advice on what he should ask (and, for example, whether he should call Mrs Clinton "Crooked Hillary" on stage).

"You're going to see a very natural and normal guy - someone who is comfortable with who he is, not someone who's highly scripted or nervous," Mr Giuliani told the Washington Post.

Where the candidates stand

Our man Anthony Zurcher has worked out where the candidates stand on key issues in relation to other world leaders.

"On refugees, for example, Donald Trump has been warning that the US policy of admitting refugees from certain regions - the Middle East or, more generally, Muslim nations - presents a serious threat to US national security. He's called for the US to suspend resettling refugees until "extreme vetting" procedures can be implemented. He asserts that nations in the Middle East must do more to create safe zones for those fleeing the violence.

"Hillary Clinton has called for an increase in the number of Syrian refugees resettled in the US from the current 10,000 annual mark to 65,000 - which, Mr Trump likes to point out, is a 550% increase. She cautions that the refugees should be "carefully vetted", but notes that current procedures already involve a multi-year application process and refugees don't know in which nation they will be settled."

Read more: Where the candidates stand

Why the moderator has such a tough job

Image copyright AP Image caption Lester Holt: Don't envy him

Just ask Matt Lauer.

Earlier this month, Lauer, Holt's NBC colleague, interviewed Mr Trump but did not pick up on his false statement saying he did not support the war in Iraq.

The backlash was brutal, and ensures the moderators of all the debates are under particular scrutiny this year. On top of that, Mr Trump has said the debates are rigged, should have no moderator and that Holt is a Democrat (he's actually a registered Republican).

Both candidates have provided plenty of work for fact-checkers during the campaign - in Mr Trump's case, he has repeatedly tried to deny the truth even when there's significant evidence to the contrary.

So trying to anticipate half-truths and non-truths, and knowing how and when to call them out, will be a thankless task.

At the very least, it should be entertaining.