Who won the debate? Harris' forceful performance rattles a defensive Trump.

Donald Trump knocked Joe Biden out of the 2024 presidential race in the last debate , but the Republican found himself repeatedly knocked on his heels Tuesday night when squaring off against his new Democratic opponent: Kamala Harris.

Then came Taylor Swift, who delivered her own version of a knock out.

Inside the debate hall in Philadelphia, Trump was on the defensive over his legal problems, election denialism, opposition from former allies and incitement of an attack on the U.S. Capitol. Even his beloved rallies become debate fodder, with Harris mocking them as full of odd digressions and so boring his supporters often leave early.

Harris came in trying to rattle and bait Trump, and often succeeded, leading to defensive, angry and rambling responses as the vice president had the upper hand throughout much of the contest. Trump repeatedly turned to immigration, his signature issue, but struggled to sustain a consistent line of attack and often leaned on familiar and false claims that drew corrections from the moderators.

Harris and Trump faced off in Philadelphia as polls show the race tied or within the margin of error in critical swing states. The candidates were under pressure to deliver strong performances during their first ever meeting .

Expectations were high for both campaigns. Harris needed to prove herself on the biggest stage yet and better introduce herself to undecided voters, while Trump faced questions of whether he could deliver a disciplined takedown of Harris’ policy positions without veering into personal attacks.

Their debate marked the biggest moment in the race for Harris since Biden dropped out nearly two months ago and she quickly secured the Democratic nomination. She energized the Democratic Party and pulled back within sight of Trump, but there have been signs that her “honeymoon” period is ending and voters are taking a closer look.

Nervous Democrats saw a significantly stronger advocate than Biden, who repeatedly stumbled when he squared off against Trump on June 27 in Atlanta. In addition to delivering a much more fluid and coherent message, Harris often looked more poised than Trump as she calmly prosecuted the case against him, prompting a series of angry outbursts.

Harris' debate performance earned an immediate thumbs up from Swift, the pop star whose support Democrats envision jolting young voters into helping them hold onto the White House.

Contrasting with Joe Biden

Harris gained the upper hand in the debate by constantly needling Trump on issues large and small, delivering somber commentary on his threat to democracy alongside mocking remarks about his obsession with Hannibal Lecter and windmills.

That she is a more formidable opponent than Biden was evident from the start, when she fielded a question about the economy and launched into her plans for the middle class before quickly pivoting to slamming what she called a “Trump sales tax,” a reference to his proposed tariffs.

Trump defended the tariffs and a host of other policies and actions as Harris kept the pressure on.

“Let’s talk about what Donald Trump left us,” Harris said at one point, listing off the dire state of the economy when he left office, the COVID-19 crisis and “the worst attack on our Democracy since the Civil War.”

The vice president went on to dismiss his “same old tired playbook.” She later zeroed on his rallies, saying people were leaving them out of “exhaustion and boredom.”

“People don’t leave my rallies,” Trump responded.

“We have the biggest rallies, the most incredible rallies in the history of politics,” he added.

ABC moderators fact check in real time

Trump tried to turn the debate to immigration, but found himself being corrected by the moderator after claiming Haitian immigrants were eating pets in Springfield, Ohio, citing comments from people on television.

“(The) Springfield city manager says there’s no evidence of that,” said moderator David Muir.

The debate moderators also corrected Trump when he said Democrats support abortion policies that would allow babies to be killed after being born, and on his claim that "crime in this country is through the roof," noting FBI statistics show violent crime dropping.

Harris came in trying to present herself as a more forward looking candidate, encouraging voters to look ahead and "turn the page."

The message was most forceful when Harris highlighted the former president's response to the Jan. 6, 2021, attack on the U.S. Capitol by a mob of his supporters.

"If that was a bridge too far for you, well there is a place in our campaign for you," Harris said, adding: “Let’s chart a course for the future and not go backwards to the past.”

Trump was pressed by the moderators and about the attack on the Capitol and his false claims that the 2020 election was stolen.

Asked if he regrets anything about Jan. 6, he defended his response and blamed former House Speaker Nancy Pelosi for a lack of security at the Capitol. He pivoted to immigration after Harris slammed his Jan. 6 response, saying migrants “are killing many people unlike J6,” when many police officers were injured and some subsequently died, along with members of the crowd.

Continuing to falsely claim “there’s so much proof” the 2020 election was stolen, Trump tried to move on from the issue by saying “you know what that doesn’t matter because we have to solve the problem that we have right now. That's old news.”

Harris kept pressing, saying Trump was "fired by 81 million people... and clearly he is having a very difficult time processing that.”

She said world leaders are “laughing at Donald Trump” and added that his comments on the election "leads one to believe that perhaps we do not have in the candidate to my right the temperament or the ability to not be confused about fact. That’s deeply troubling and the American people deserve better.”

Trump couldn’t help responding, touting his relationship with Viktor Orban, the authoritarian leader of Hungary.

This article originally appeared on USA TODAY: Who won the debate? Harris' forceful performance rattles a defensive Trump.