TOP OBAMA ADVISER: Here's the blueprint Hillary Clinton should follow for success in the first debate

David Plouffe, President Barack Obama's 2008 campaign manager, told Business Insider on Monday that Hillary Clinton can't be too "overanxious" to attack Donald Trump in the night's first presidential debate.

He added that Clinton must speak "from the gut" about both her motivations to be president and about how her ideas would improve the lives of average Americans.

"That's far and away the most important thing," he said. "I think the most important thing is for undecided voters to have a better sense of her the person, kind of what her motivations are. I think for members of the so-called Obama coalition, who aren't as passionate about her candidacy, to get them more excited. And I think to show that there is still a gap between her and Donald Trump in terms of who's fit to be commander in chief."

If she manages to do that, the first debate should be a success, he said.

She'll have to "look for opportunities" when it comes to going on the offensive against the Republican nominee.

"When it comes to Trump, you can't overdo it," he said. "If you are overanxious or swerving out of the lane to get him to trip up, that probably won't work."

"So you can prepare and practice, and sometimes your stand-in will say what the candidate says at the exact moment, but usually not," he continued. "So there's just judgment on the stage about when to engage, when to fact-check, when to really have a moment."

A major difference between preparing for Trump as opposed to candidates for whom Plouffe prepared Obama — Sen. John McCain of Arizona, the 2008 GOP nominee, or former Gov. Mitt Romney of Massachusetts, the 2012 GOP standard-bearer — is that it's up in the air which version of the Manhattan billionaire will be on stage at Hofstra University on Monday night.

"Trump might be very docile or sedated and try and just nice-guy his way through the debate," he said. "I think authenticity matters a lot in politics, so that's a big departure from how he's conducted himself. So I'm not so sure in the long run that works, but you've got to prepare for multiple Trumps in multiple moments."

But Clinton must focus on what she is "trying to do as president before you even get to your opponent," he added.

"And to understand that these aren't policy — policy is important and issues are important — but these are as much about performance," he continued.

David Plouffe. Charles Rex Arbogast/AP

Plouffe said that aspect was "always hard for" Obama because of his style of building up lengthier arguments.

"Because he's a lawyer by training and he likes to build up to his closing argument," Plouffe said.

Looking back at how he helped Obama prepare for his first presidential debate in 2008 against McCain, Plouffe said there was a major focus on proving that the then senator from Illinois was prepared to be commander in chief. It's somewhat similar to what Trump is facing in Monday's titanic event.

"We were doing well in the race, [but] we had to cross a bar in terms of being prepared to be commander in chief," he said. "And that was a debate centered on national security, so it was a great opportunity."

"I mean, Trump has to do a similar thing, but I think he's got more business," he continued. "I will say this ... I've helped prepare for six of these — these are human beings up there on that stage. And you just don't know what's going to happen. They are not automatons. Things happen in all these debates that you don't prepare for, both good and bad."

In an unprecedented way, the moderator of Monday's debate, NBC's Lester Holt, is under more pressure from external sources than any moderator before.

Plouffe said the performance of the moderator — and how he decides to fact-check the event — "should be the last thing on" the mind of either candidate.

"He knows what he needs to do," Plouffe said. "It's an interesting debate to me because I've watched every debate multiple times to get ready for the prep we have to do, and no moderator just reads the queue cards. Anybody can do that."

"But, you know, they will have a light touch and decide where to move the discussion," he continued. "I'm sure he'll do a great job. But if you're a candidate, you can't worry about what the moderator does. You've got to take care of your own business."

Holt selected "America's Direction," "Achieving Prosperity," and "Securing America," as the three topics for the debate, leaving plenty of room for broad questioning throughout the 90-minute affair, which will be broken down into six 15-minute segments.

Plouffe said the broadness of the debate is "good practice" for the next two, which include a more open town-hall event.

"You've got to look at each [topic] and understand you want to be responsive to the questions but you also have to understand where you want to drive the discussion, both in terms of the contrast with your opponents but in terms of your own plans," he said. "This is a broad ranging set of issues."

"Now, the town hall is the one that's the most complicated to prepare for because you know you're getting citizens," he continued. "Citizens ask questions in ways that are different than journalists. It tends to be broad reaching, and you always tend to have a question or two you didn't prepare for. I think that's the most engaging debate for the American people.

"But this is the big one, because the audience is going to be huge. And, you know, I think it's your best way to communicate directly with voters. The filter is important, but most Americans that you care about are going to be watching this debate, which is amazing."