STEVE INSKEEP, HOST:
Now, the first presidential debate comes Monday night. NPR national political correspondent Mara Liasson is reporting on the challenge for both candidates and today examines Trump.
MARA LIASSON, BYLINE: Among the tens of millions of people watching on Monday night, many of them will, believe it or not, be getting their first real look at Donald Trump. So Trump has to decide what he wants to show them. He told Bill O'Reilly on Fox News this week that he has a lot of lines of attack against Hillary Clinton.
(SOUNDBITE OF TV SHOW, "THE O'REILLY FACTOR")
DONALD TRUMP: I can talk about her deleting emails after she gets a subpoena from Congress and lots of other things. I mean, I can talk about her record, which is a disaster. I can talk about all she's done to do help ISIS become...
BILL O'REILLY: Well, I expect you'll do that anyway, though. Right?
TRUMP: ...The terror that they've become. And I will be doing that.
LIASSON: Trump's campaign manager, Kellyanne Conway, says Trump knows what he wants to do on Monday.
KELLYANNE CONWAY: Mr. Trump's goal in the first debate is to win and to show Americans what he showed them in the earlier NBC Commander-In-Chief Forum, which is he's ready on Day One to lead as their commander in chief and as the president of the United States, why he is the best person to lead the country forward, to break from the past and its failed policies and really to move on from the exhaustion and the fatigue of Hillary Clinton.
LIASSON: So change versus more of the same will be Trump's theme. As for his style and delivery, I asked Alex Conant who was Marco Rubio's spokesman in the primaries and learned a lot about how Trump debates.
ALEX CONANT: Don't ever underestimate Donald Trump. He's a very gifted showman, and he has a very salient message. And it makes for tough debate, especially if you let him do it on his terms.
LIASSON: When the debates are about personalities and personal records, Conant learned, Trump is very comfortable. But...
CONANT: When you get him talking in-depth about his own policy proposals, I think it becomes very clear very quickly that he hasn't spent a lot of time studying public policy over the last couple of years. And those can turn into bad moments for him.
LIASSON: Moments that Hillary Clinton will be ready to exploit - and that raises a big challenge for Trump. This is the first one-on-one debate of Trump's entire, short political career. He has never been alone on a debate stage with a single opponent.
Trump has one big thing to accomplish on Monday. He needs to convince people that he's capable of being president of the United States. Right now, a majority of voters don't think he has the qualifications or the temperament. But Trump also has some big advantages - No. 1 - low expectations.
CONANT: If Donald Trump can stand on the debate stage for two hours and not lose his temper and come across as a reasonable person, he'll have a good night. If Hillary Clinton can stand on the debate stage and convince people that she's not a liar, she'll have a great night. But clearly, the former is easier than the latter.
LIASSON: People don't expect a lot of substance from Trump or even a strong command of policy, says Kevin Madden who was campaign spokesman for Mitt Romney and George W. Bush. Madden thinks Trump just has to hold his own.
KEVIN MADDEN: Donald Trump has an expectation of being somebody who causes a lot of controversy. If he were to defy some of those expectations - not have outrageous moments, not be overbearing, not be controversial - in many ways, it will help him, you know, be graded against those expectations.
LIASSON: That Trump is graded on a curve drives Democrats nuts. But there is one area where expectations are very high for Trump. People expect him to be aggressive and to dominate the debates the way he did during the primaries when he eviscerated one opponent after another. And Trump will be doing something no one else has done before. He'll be debating the first female nominee for president. How that plays out, no one knows.
And Trump has already been working the refs, just in case he doesn't do so well. He's claimed the only way he can lose the election is if it's stolen from him. Now he's saying the debates are already rigged against him. He told Bill O'Reilly that Lester Holt, the first debate moderator, is biased.
(SOUNDBITE OF TV SHOW, "THE O'REILLY FACTOR")
TRUMP: It's a phony system. Lester's a Democrat. I mean, they're all Democrats. OK? It's a very unfair system.
LIASSON: In fact, Lester Holt, an experienced journalist, is not a Democrat. He's a registered Republican since 2003 according to New York State voter registration documents. There are really three phases of a debate - pre-game goal-setting, which Trump has been busy doing, the debate itself and the post-game battle to control perceptions of who won and who lost. So neither candidate is taking any chances. After all, close to a hundred million people could be watching.
Mara Liasson, NPR News, Washington. Transcript provided by NPR, Copyright NPR.