A former prosecutor, Harris, 59, appeared to get under the former president’s skin repeatedly, prompting a visibly angry Trump, 78, to deliver a series of falsehood-filled retorts.

At one point, she brought up Trump’s campaign rallies, goading him by saying that people often leave early “out of exhaustion and boredom.”

Trump, who has been frustrated by the size of Harris’ own crowds, said, “My rallies, we have the biggest rallies, the most incredible rallies in the history of politics.”

He then pivoted to an unsubstantiated claim that Haitian immigrants in Springfield, Ohio, are “eating the pets” of residents.

“Talk about extreme,” Harris said, laughing.

The candidates clashed over issues such as immigration, foreign policy and healthcare, but the debate was light on specific policy details.

Instead, Harris’ forceful approach succeeded in putting the focus on Trump, leaving her allies jubilant and some Republicans acknowledging Trump’s struggles.

“Trump missed an opportunity to stay focused prosecuting the case against Biden-Harris on the economy and border, and instead took her bait and chased down rabbit holes on election denialism and immigrants eating our pets,” said Marc Short, who served as chief of staff for Trump’s former Vice President Mike Pence.

Online prediction market PredictIt’s 2024 presidential general election market showed Trump’s likelihood of victory declining during the debate, to 47% from 52%. Harris’ odds improved to 55% from 53%.

In a sign of confidence in the debate’s outcome, Harris’ campaign challenged Trump to a second debate immediately.

Trump, who has spent weeks launching personal attacks on Harris including racist and sexist insults, largely avoided that pattern during the debate’s early moments but quickly became agitated under Harris’ offensive.

Trump was asked by the moderators about one of those attacks, when he told an event with Black journalists in July that Harris had recently “become a Black person.”

“I couldn’t care less,” he said. “Whatever she wants to be is OK with me.”

Harris, who has both Black and South Asian heritage, responded, “I think it’s a tragedy that we have someone who wants to be president who has consistently over the course of his career attempted to use race to divide the American people.”

She criticised Trump over his criminal conviction for covering up hush money payments to a porn star as well as his other indictments and a civil judgment finding him liable for sexual assault. Trump has denied wrongdoing and again accused Harris and the Democrats of orchestrating all of the cases without evidence.

Trump also repeated his false claim that his 2020 election defeat was due to fraud, called Harris a “Marxist” and asserted falsely that migrants have caused a violent crime spree.

With eight weeks to go before the election, and days until early voting starts in some states, the debate — the only one scheduled — presented both opportunities and risks for each candidate in front of a televised audience of tens of millions of voters.

A surprise handshake

The debate got under way at 9pm ET (6am PST on Wednesday) with a surprise handshake between the two opponents, who had never met before. Harris approached Trump at his lectern, introducing herself by name, in what was the first handshake at a presidential debate since 2016.

The encounter was particularly important for Harris, with opinion polls showing that more than a quarter of likely voters feel they do not know enough about her. Harris entered the race only seven weeks ago after President Joe Biden’s exit.

Harris delivered a lengthy attack on abortion limits, speaking passionately about women denied emergency care and victims of incest unable to terminate their pregnancies due to statewide bans that have proliferated since the US Supreme Court eliminated a nationwide right in 2022. Three Trump appointees were in the majority of that ruling.

She also claimed Trump would support a national ban. Trump called that assertion untrue but declined to say explicitly that he would veto such a law.

Trump, who has sometimes struggled with messaging on abortion, said falsely that Harris and Democrats support infanticide, which — as ABC News moderator Linsey Davis noted — is illegal in every state.

Harris also sought to tie Trump to Project 2025, a conservative policy blueprint that proposes expanding executive power, eliminating environmental regulations and making it illegal to ship abortion pills across state lines, among other right-wing goals.

Trump retorted that he has “nothing to do” with Project 2025, though some of his advisers were involved in its creation.

Ron Bonjean, a Republican strategist, said Trump “didn’t do himself any favours” but added that it remains unclear whether Harris’ performance will change the race’s dynamics. Polls show a vast majority of Americans have made up their minds, leaving a small sliver of undecided voters up for grabs.

Clashes on economy, foreign policy

The candidates opened the debate by focusing on the economy, an issue that opinion polls show favours Trump.

Harris attacked Trump’s intention to impose high tariffs on foreign goods — a proposal she has likened to a sales tax on the middle class — while touting her plan to offer tax benefits to families and small businesses.

Trump criticised Harris for the persistent inflation during the Biden administration’s term, though he overstated the level of price increases. Inflation, he said, “has been a disaster for people, for the middle class, for every class.”

The candidates also exchanged barbs over the Israel-Gaza war and the Russian invasion of Ukraine, though neither offered specifics on how they would seek to end each conflict.

Harris accused Trump of being willing to abandon US support for Ukraine to curry favour with Russian President Vladimir Putin, calling Trump a “disgrace,” while Trump claimed Harris “hates” Israel — an assertion she rejected.

Presidential debates do not necessarily change voters’ minds, but they can be deeply consequential. Biden’s poor performance against Trump in June led him to abandon his campaign on July 21.

In a contest that could again come down to tens of thousands of votes in a handful of states, even a small shift in public opinion could alter the outcome. The two candidates are effectively tied in the seven battleground states likely to decide the election, according to polling averages compiled by the New York Times.

The debate, hosted by ABC News, took place at the National Constitution Center in Philadelphia. As agreed by the campaigns, there was no live audience and candidates’ microphones were muted when it was not their turn to speak.