Vice President Harris’s best chance to score points against President Trump at Tuesday night’s debate may be if she is able to goad the former president into getting angry or emotional. The last time Trump did such a thing on a debate stage, when in 2020 he squared off against President Biden with open microphones and repeatedly interrupted him, Mr. Biden was widely considered the winner.

Ms. Harris and Trump will meet at the National Constitution Center at Philadelphia on Tuesday at 9 p.m. for their first — and likely only — debate of the 2024 election. The vice president, who has largely avoided interviews and any unscripted appearances since Mr. Biden stepped aside from campaigning in her favor, will be under enormous pressure to show voters she can function in an unscripted, live television environment.

Trump, on the other hand, is universally well known by voters and may have less to lose. Only last week, he gave a rambling, 45-minute press availability during which he denounced, in great detail, various women who had accused him of sexual assault many years ago. After dominating political discourse for the last eight years, the vast majority of voters say they have already made up their minds about him.

During the first presidential debate of the 2020 general election, Trump came out swinging against Mr. Biden — interrupting, yelling, and appearing unfocused and emotional. By the end of the debate, 60 percent of viewers said Mr. Biden had won, compared to 28 percent who said the same of Trump, according to a CNN poll. 

While the second debate was canceled due to Trump’s Covid diagnosis, the final debate saw a more measured Trump. The 45th president seemed more reluctant to appear as aggressive as he had in the first, clearly learning from the poll numbers he saw after the first forum. 

Ms. Harris’s campaign team is hoping that there can be a repeat of the first 2020 debate. If Trump rudely interrupts her, she can portray herself as more of a policy-focused leader, and possibly can set the narrative for the rest of the election. 

During her debate against Vice President Pence in 2020, Ms. Harris repeatedly said, “I’m speaking,” and, “Excuse me, I’m speaking,” in a clearly rehearsed routine designed to make Mr. Pence appear like he was being rude and condescending to a woman.

Tuesday night’s debate is an opportunity for both Ms. Harris and Trump “to explain to the country what it is they want to do as president, and there’ll be a clear contrast on that stage,” a senior Harris campaign advisor, Ian Sams, told Fox News on Tuesday. 

“Vice President Harris represents the future. She wants to turn the page on the past. She represents a new way forward for this country, while Donald Trump represents something old, something stale, something that people are ready to move on from,” Mr. Sams added. “He’ll have to answer for some of his positions.”

He went on to say that Trump will have to explain his concrete policy positions that will help the American people, which Mr. Sams said was unlikely to happen because of what he called Trump’s penchant for airing personal grievances. 

“I think he’s gonna have to figure out for just a few minutes during this debate whether he can talk about anything other than himself. I think he wants to spend more time complaining about her crowd sizes compared to his,” Mr. Sams said.

For the Trump campaign, they say the former president is going to focus on pocketbook issues that Americans care most about — inflation, immigration, and crime. In a memo shared with The New York Sun on Tuesday that was addressed to the ABC News debate moderators — David Muir and Linsey Davis — Trump’s campaign staff said the American people deserved to know the truth about Ms. Harris’s “preposterous claims regarding public safety.”

“We felt it necessary to make you aware that the actual facts show conclusively and irrefutably that Kamala Harris has presided over a staggering increase in violent crime and that illegal border crossings remain at historic highs,” the campaign wrote. It says that Ms. Harris, as the so-called border tsar, has presided over the most devastating “border disaster” in American history, including the release of more than 10 million migrants into the country. The campaign says these migrants have contributed to violent crime rates across the nation. 

The problem for any hopes of a strong emotional reaction from Trump or any kind of interrupting is that ABC News and the Trump campaign insisted that both candidates’ microphones be muted while the other is speaking — which is a rule that Mr. Biden had agreed to during the CNN debate that ended his re-election bid, and that Ms. Harris tried to get reversed, without success. It will help prevent interrupting from the 45th president, and likely robs Ms. Harris of her “I’m speaking” moments from 2020. 

The vice president claims she’s the underdog in the 2024 race, with polls showing her post-announcement bump leveling off, if not fading, and election models giving Trump a slight edge in the Electoral College. An aggregation of recent polls shows the race to be a toss-up, when polling in the seven swing states is taken into account. 

While Ms. Harris is sitting on a mountain of cash and an excited Democratic base, it is a large chunk of swing voters in key battleground states, who are not yet sure what to make of Ms. Harris, that will be her target audience at the debate tonight. 

According to polling, voters have already made up their minds about what they think of Trump and his policies, and want to learn more about the vice president. A recent New York Times–Siena College poll found that nearly one-third of voters want to know more about Ms. Harris before making a decision in November. 

“I don’t know what Kamala’s plans are,” a small-business owner in Tennessee, Dawn Conley, told the Times. “It’s kind of hard to make a decision when you don’t know what the other party’s platform is going to be.”

In critical voting blocs, voters are hungry for more information about Ms. Harris. A decent number of independents, undecided voters, voters who did not cast ballots in 2020, Hispanics, and young voters all say they don’t have a favorable or unfavorable view of Ms. Harris relative to Trump, who is more of a known quantity for those same demographics.