For Kamala Harris, Tuesday night's presidential debate with former U.S. president Donald Trump could be a significant moment of opportunity for the vice-president, but also, perhaps, a significant risk. 

"I do think this is a debate about Kamala Harris more than it's a debate about Trump," said Alan Schroeder, professor emeritus at Northeastern University's school of journalism, and an expert on presidential debates.

With Trump such a known commodity, the debate — the first and possibly only contest between the two current candidates — could offer Harris the occasion to grow her level of support. On the flip side, she could alienate voters if she does not perform well.

"Trump has been so dominant on the American political stage for the past decade, really," Schroeder said. "And now it's about someone else."

Trump won't have Biden as distraction

That could be an advantage for Harris, says Schroeder, because there will be more attention on her. But it also means more pressure and "the absolute need for her to have a successful debate, in order to capitalize on this momentum."

But for Trump, experts say a poor performance — which may include his habits of avoiding answering questions, making false statements and repeating personal attacks he's made against Harris on the campaign trail — could have more resonance this time without the distraction that President Joe Biden's performance provided last time.

"Biden was so awful that it actually overwhelmed the fact that Trump did not have a good debate performance either," said Patrick A. Stewart, a political science professor at the University of Arkansas, and the author of The Audience Decides: Applause-Cheering, Laughter, and Booing during Debates in the Trump Era.

WATCH | Key moments from the Trump-Biden debate: 

Key moments from the Biden-Trump debate

U.S. President Joe Biden and former president Donald Trump squared off in a debate in Atlanta that aired on CNN. Here are some of the major moments — including when Trump took advantage of a verbal fumble from Biden, as well as the current president accusing his predecessor of having 'the morals of an alley cat' regarding his ongoing criminal and civil legal issues.

Stewart also believes Trump, who has "never been a policy guy," may also be judged on whether he still has the same vigour he's had in prior debates.

"Is it still the Trump that we know from back in 2016 and 2020 where he was sharp, was on his game as far as verbally being able to come at people and verbally attack them," he said. "Or will he have lost a little bit of steam?"

The debate, which is scheduled for Tuesday at 9 p.m. ET, is expected to last 90 minutes and is being moderated by ABC News anchors David Muir and Linsey Davis, with no studio audience.

It may not have the same immediate impact as Trump's debate against Biden, whose poor performance raised questions about his cognitive abilities, and eventually led to him stepping down as the Democratic presidential candidate before being replaced by Harris. 

Still, with polls suggesting the race is tied, either candidate's debate performance could move the needle among those undecided voters who will be key in determining the outcome of the election. 

"I think this will be sort of a big, marquee moment for people to begin to arrive at a decision," Schroeder said.

WATCH | Harris and Trump prepare for the upcoming debate: 

Donald Trump and Kamala Harris gear up for Sept. 10 debate

A jam-packed summer in U.S. politics comes to a close as Kamala Harris and Donald Trump officially confirmed their places on the Nov. 5 presidential ballot. Power & Politics does a deep dive into the U.S. election and looks ahead to their Sept. 10 debate.

Harris may focus on Trump policy failures, abortion

For weeks, Harris has reportedly been preparing for this debate, which has included mock debate sessions. She's expected to focus on what her team perceives as Trump's policy failures as president, which include the U.S. border wall, infrastructure and the COVID-19 pandemic, Reuters reported.

She may also focus on abortion and the reversal of Roe v. Wade during Trump's presidency, an issue widely perceived as a liability for Republicans and Trump, whose U.S. Supreme Court appointments led to the reversal.

Robert Rowland, a professor of rhetoric and political communication at the University of Kansas, says that along with some policies, predicts Harris will also focus on suggesting Trump is a "scam artist" who "doesn't care about ordinary people."

In Harris, Trump will be facing a opponent known for her discipline, something she's shown on the campaign trail by sticking to the same talking points. A potential weakness for Trump during the debate, some experts say, is his  tendency to engage in rambling, stream of consciousness answers that touch on a variety of subjects — something he has recently boasted about and referred to as "the weave."

But Harris herself has been criticized for some of her own rambling answers during events, or as noted by the New York Times following her CNN interview, "she can sometimes deliver discursive answers that ramble and zigzag."

Stewart suggested Harris is also at a disadvantage in that she hasn't yet had a full vetting and "really hasn't faced any individuals up until this point" in the campaign.

Harris 'can't show any nerves'

While Harris has been involved in other debates, including those in the 2020 Democratic primaries and a vice-presidential debate, this will be her biggest audience yet. Schroeder points out this debate will be in a different league, and Trump has experienced such debates six times.

"I think inexperience at that level, playing the game at this level, is something that is really hard to do," he said. "I think she can't show any nerves. She can't show any sign of intimidation or fear on that stage."

Harris has also only faced one sit-down interview since being named a candidate, meaning she will need to be prepared to face attacks by Trump, but also questions from the debate moderators.

WATCH | Harris talks policy, cabinet plans in 1st big interview:

Kamala Harris talks policy, cabinet plans in 1st big interview

In the first big interview of her presidential campaign, Kamala Harris told CNN she plans to put a Republican in her cabinet. She also defended the current U.S. policy surrounding the Gaza war, and laid out her plans to tackle affordability.

Those questions will likely include topics such as the Biden administration's record and accusations of flip-flopping on some key policy initiatives. For example, she has previously indicated support for a ban on fracking and the decriminalization of illegal border-crossings, but she and her campaign have said that she no longer holds those views.

"She's going to be challenged on not only her previous record, but [the] Biden administration record in general," Schroeder said. "It'll be interesting to see how she deals with that."

It's that record, Republican operatives have suggested, that Trump needs to focus on, to try to rattler her on policy. 

"But that's not Trump's strong point," said Stewart.

'Trump's gonna Trump'

Marc Thiessen, a speechwriter for former U.S. president George W. Bush, wrote in a column for the Washington Post that Trump needs to take advantage of the fact that many undecided voters don't like the direction of the country.

And Trump needs to remind voters of the policies that were popular during his administration, Thiessen wrote.

He also said Trump needs to tie Harris to parts of Biden's record that remain unpopular, such as the spike in inflation, as well as zeroing in on Harris's flip-flops. He must also avoid reminding voters about why many people don't like him, which would also mean avoiding personal attacks on Harris.

"With one disciplined debate performance, Trump helped knock Biden out of the race. On Tuesday night, he has a chance to do the same to Harris," Thiessen wrote.

WATCH | How both candidates are courting the working class: 

How are Trump, Harris courting the U.S. working-class vote? | Canada Tonight

Thomas Frank, political analyst and historian, talks about how both Donald Trump and Kamala Harris are trying to win the working-class vote in the U.S., and how the upcoming Sept. 10 presidential debate could be as consequential as the last.

Yet that suggests some kind of strategy on Trump's part — something he hasn't appeared to have used in previous debates, according to Schroeder.

"He doesn't really go in with a game plan. He doesn't work on specific lines or specific lines of attack," Schroeder said. "He doesn't seem to be able to tailor an argument against a particular candidate. It's always just to strafe them with as much ammo as he can."

Rowland says Trump only has one style, and that since it's not focused on the issues, he's able to use it regardless of the questions. 

"The disadvantage is, there's a point where he offends people," he said.

"Most of that is baked in. But I think, with college educated women especially, it's going to remind them why they voted against him in the last election."

Trump focusing on specific policies instead of going for the personal attack would show a "level of growth," according to Stewart, who says he's not expecting that. 

"Trump's gonna Trump," Rowland said.  

"The one thing that would throw him off his game is if she just maintains an even keel."