NOTE: NBC Chicago will provide live coverage of the debate, which begins at 8 p.m. CT. Watch here.

While many will focus on the word choice during Tuesday night’s presidential debate between Vice President Kamala Harris and former President Donald Trump, another element will quietly emerge that could play a major role.

Body language.

Obviously, there will be a clear gender dynamic on stage on Tuesday night.

The candidates — who have never met in person before — are expected to remain behind their podiums. But Republicans are hoping Trump will avoid any other provocations, such as pointing, shouting or otherwise approaching Harris in a way that could be off-putting to suburban women or other swing voters.

Harris, too, will face unique challenges related to her race and gender as voters weigh whether to make her the nation’s first female president. Some voters still say they’re uncomfortable with the idea. If she comes across as angry, she risks playing on racist clichés about black women.

From her early campaigns in California to her role as President Joe Biden’s running mate, Harris has developed an aggressive but measured approach to debates.

She tries to combine jokes with details that build toward a larger story. She may shake her head to show her disapproval while her opponent is speaking, counting on viewers to see her reaction in split screen.

She also has a handy tactic for turning debates in her favor: she says she likes to answer a question while gathering her thoughts to explain a changing position or defend a previous one.

This is not the first time Trump has debated a candidate seeking to become the country’s first female president.

As Trump and Harris prepare for their first — and possibly only — debate, his three meetings with Clinton in 2016 illustrate the challenges both candidates face in what appears to be another close election.

Harris faces a skilled and experienced debater who can shake his opponents to their core with a barrage of insults and interruptions, yet who at the same time exudes an unwavering confidence and conviction.

And Trump will be dealing with a prosecutor who has a long-standing reputation for hitting hard.

While gender dynamics play a role, don’t underestimate the importance of the age difference either.

Harris is nearly two decades younger than Trump, 78. Age was seen as a political advantage for Trump when he faced Biden, 81, but the situation is now reversed for Harris, 59. If he wins, Trump would be the oldest U.S. president ever elected.

When you ask Trump’s previous debate opponents what they were watching for Tuesday night, many say the same thing: Pay attention to what he says or does that Harris couldn’t possibly prepare for.

Trump is the ultimate wild card who has achieved enormous political success by ignoring the traditional rules of politics. He will say or do whatever he thinks is best at the time. And Harris, who has spent several days preparing for the debate, can’t plan for everything.

Trump’s own team doesn’t know what he’s going to do or say on any given day. That’s incredibly risky for Trump. But it also puts enormous pressure on Harris.

Donald Trump’s campaign team says his unpredictability will give him a significant edge in Tuesday’s debate.

“You can’t prepare for President Trump. There’s just no way to do that,” senior campaign adviser Jason Miller told reporters on a call Monday, comparing the challenge facing Vice President Kamala Harris to “a boxer trying to prepare for Floyd Mayweather or Muhammad Ali.”

“You just don’t know what angle they’re going to attack you from,” he said.

Still, aides said, Trump will focus on trying to tie Harris to the Biden administration’s least popular policies. Trump will try to blame her not just for the border, inflation and foreign policy, but also for other things that happened while she was in office, such as the catastrophic Maui fire last year.

“Kamala Harris is the boss of everything this administration has to offer,” Miller said.

Former Rep. Tulsi Gabbard, who ran against Harris in the 2020 Democratic primary and helped Trump prepare, said his tone won’t change this time around because he’s running against a woman.

“President Trump respects women and doesn’t feel the need to patronize or speak to women any differently than he would speak to a man,” she said. “So he’s speaking to the American people, he’s speaking about Kamala Harris’ record, and he’s comparing and contrasting that with his record.”