Presidential debates are significant in American politics, and the upcoming face-off on Tuesday night between Donald Trump and Kamala Harris holds particular importance as it is their only currently scheduled debate.

Joe Biden’s poor performance in the first presidential debate in late June created significant pressure within the Democratic Party, ultimately leading to his decision to not seek re-election.

Kamala Harris has been the vice president for over three years and a presidential candidate for seven weeks. However, she is still relatively unknown to many Americans. According to a recent survey by The New York Times, 28% of likely November voters said they need to know more about the Californian.

The latest poll indicated that the race is too close to call, which aligns with other recent surveys at both national and battleground state levels. Despite the historic turbulence of the 2024 presidential campaign, the American electorate remains sharply and narrowly divided.

That underscores the importance of Tuesday night’s debate, where even small shifts in the mood of the electorate could be the difference between victory and defeat for the candidates.

For Harris, the Philadelphia showdown presents an opportunity to elaborate on the details before a massive audience, despite facing verbal attacks from her Republican opponent.

This opportunity is not without risks, however, as Harris could define herself – and her positions – in ways that damage her electoral prospects. She has struggled in the past with answering pointed questions under pressure, and her reluctance to sit for media interviews in the opening weeks of her campaign has denied her the opportunity to hone her linguistic chops.

Although she has tried to present herself as the change candidate in this election, the moderators – and the former president – are likely to press her to defend the Biden administration’s record, particularly on areas where polls show Democrats are weak, such as border security and inflation.

She will also have to explain why she has renounced some of the more liberal policies she embraced during her unsuccessful bid for the 2020 Democratic presidential nomination. She recently has walked back her positions on a fracking ban, decriminalising border crossing and nationalising health insurance, among others.

She has explained these changes as ones made to reflect new circumstances – but they may be viewed by some voters as moves born of political expediency.

For Trump, the debate presents an opportunity to wrest back the initiative in this campaign after a month where the Democrats – with their new nominee and high-energy convention – dominated political headlines. He has a history of thriving in the spotlight and setting the terms of political conversation that keeps his opponents off-balance and his issues – notably on immigration and trade, where his positions have broad popular support – at the forefront of political discussion.

The former president has his own potential pitfalls on Tuesday, however. His uneven performance during his June debate with Biden drew little scrutiny because of his opponent’s sometimes catastrophic verbal miscues. Harris is sure to present a more nimble opponent, and his answers will have to be sharper.

During a New York economic forum last week, he was unable to offer a clear explanation for his childcare policies. Such verbal meandering during the debate will provide Democrats with a wealth of campaign fodder.

Trump must also tread carefully when sparring with the vice-president – only the second woman presidential nominee and the first of colour. If he comes across as domineering or belittling, he could further damage his already weak support among female voters.