The hidden part of the Trump-Harris debate that could play a big role

NOTE: NBC Chicago will offer live coverage of the debate as it begins at 8 p.m. CT. Watch here.

While many will be focused on the word choice being used during Tuesday night's presidential debate between Vice President Kamala Harris and former President Donald Trump, another element will quietly unfold that could play a big role.

Body language.

There will, of course, be an obvious gender dynamic on stage Tuesday night.

The candidates — who have never met in person before — will be expected to stay behind their podiums. But Republicans are hopeful Trump will avoid any other provocations like pointing, yelling or otherwise approaching Harris in a way that might be off-putting to suburban women or other swing voters.

Harris, too, will face unique challenges related to her race and gender as voters consider whether to make her the nation’s first female president. Some voters still say they’re not comfortable with the idea. If she comes across as angry, she risks playing into racist tropes about Black women.

From her earliest campaigns in California to her serving as President Joe Biden’s running mate, Harris has honed an aggressive but calibrated approach to debates.

She tries to blend punch lines with details that build toward a broader narrative. She might shake her head to signal her disapproval while her opponent is speaking, counting on viewers to see her reaction on a split screen.

And she has a go-to tactic to pivot debates back in her favor: saying she’s glad to answer a question as she gathers her thoughts to explain an evolving position or defend a past one.

It won't be the first time Trump has debated a candidate looking to become the nation's first female president.

As Trump and Harris prepare to debate for the first — and potentially only — time, his three meetings with Clinton in 2016 illustrate the challenges facing both candidates in what is again shaping up to be an extremely close election.

Harris will face a skilled and experienced debater who excels at rattling his rivals with a barrage of insults and interruptions, while projecting unflappable confidence and conviction.

And Trump will be up against a longtime prosecutor known for landing pointed punches.

While the gender dynamic looms, do not underestimate the significance of their age difference, either.

Harris is almost two decades younger than the 78-year-old Trump. Age was viewed as a political advantage for Trump when he was facing the 81-year-old Biden, but the situation is now reversed against the 59-year-old Harris. If he wins, Trump would be the oldest U.S. president ever elected.

If you ask Trump’s previous debate opponents what they’re watching for on Tuesday night, many say the same thing: Look out for the thing he says or does that Harris can’t possibly prepare for.

Trump is the ultimate wild card who's found tremendous political success by ignoring the traditional rules of politics. He will say or do whatever he thinks is best in the moment. And Harris, who has dedicated several days to debate prep, can’t make a plan for everything.

Trump’s own team doesn’t know what he’ll 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 says his unpredictability will give him a major leg up in Tuesday’s debate.

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

“You just, you don’t know what angle they’re going to come at you with,” he said.

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

“Kamala Harris owns everything from this administration,” Miller said.

Former Rep. Tulsi Gabbard, who competed against Harris in the 2020 Democratic primaries and has been helping Trump prepare, said that his tone will not change this time because he is facing a woman.

“President Trump respects women and doesn’t feel the need to be patronizing or to speak to women in any other way than he would speak to a man," she said. “So he is speaking to the American people, he is speaking to Kamala Harris’ record, and comparing and contrasting that with his record of success.”