NEW YORK (AP) — He claimed she would raise taxes and accused her of supporting open border policies that allowed an influx of migrants into the country. He blamed her for a litany of the current administration's failures and cast her potential presidency as four more years of the same.

Donald Trump wasn't facing Vice President Kamala Harris. It was Hillary Clinton on the debate stage.

As Trump and Harris prepare to debate for the first — and potentially only — time Tuesday, 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. He again faces a woman who would become the country's first female president, and must contend with the underlying gender dynamics at play.

Trump started out on good behavior

During their first 2016 debate in late September, moderated by NBC's Lester Holt, Trump began on his best behavior. He and Clinton warmly shook hands after taking the stage and Trump, in his first answer, said he agreed with his rival when it came to the importance of affordable childcare.

After referring to the former first lady, senator, and secretary of state as "Secretary Clinton," he checked to make sure she approved.

"Yes? Is that ok? Good. I want you to be very happy. It's very important to me," he said, drawing laughs from the audience and Clinton herself. (In later debates, he called her "Hillary," while she consistently used "Donald.")

It was Clinton who took the first digs of the night when she criticized the then-reality TV star and real estate developer for supporting "Trumped-up trickle-down" economics and said their different perspectives were borne from the fact that Trump had received millions of dollars from his wealthy father, while hers had worked hard printing draperies.

In the audience, she said, was a worker who accused Trump of stiffing him on bills.

But as the debate wore on, Trump became more combative as he pressed Clinton on why she hadn't done the things she was proposing as a candidate for president during her decades of public life.

"Typical politician: All talk, no action. Sounds good, doesn't work. Never gonna happen," he said.

Clinton's strategy: laugh it off

Clinton's strategy in responding to Trump's attacks was clear from the beginning: Don't get rattled. Laugh it off.

She never appeared flustered and instead smiled widely as she dismissively brushed off what she at one point cast as Trump "saying more crazy things."

"Well here we go again," she said in response to more insults in the second debate.

"No wonder you've been fighting ISIS your entire adult life," Trump quipped at one point as he tried to cast Clinton as an "all talk, no action" politician, of the group that formed in 2013.

"I have a feeling that by the end of this evening, I'm going to be blamed for everything that's ever happened," Clinton responded with a smile.

"Why not?" Trump answered.

Trump, meanwhile, sought to turn the arguments she made against him back onto her.

"I have much better judgment than she has…. I also have a much better temperament than she has," he declared. "I think my strongest asset — maybe by far — is my temperament. I have a winning temperament."

'You ought to be ashamed of yourself'

The second debate between Trump and Clinton was far more combative. The town hall came just two days after the release of the "Access Hollywood" tape in which Trump bragged about sexually assaulting women.

With his campaign in freefall and top Republicans urging him to leave the race, Trump invited women who had accused former President Bill Clinton, Hillary Clinton's husband, of sexual misconduct, creating a spectacle as the women sat in the audience in the debate hall and spoke at a press conference beforehand.

There was no handshake this time, and the debate quickly devolved into accusations as Trump insisted what former president Clinton had done was "far worse" than his self-described "locker room talk."

"Bill Clinton was abusive to women. Hillary Clinton attacked those same women and attacked them viciously," he said. "I think it's disgraceful, and I think she should be ashamed of herself."

Later, Trump zeroed in on the thousands of hacked emails that Wikileaks had begun to publish the day of the tape's release, as well as Clinton's use of a personal email server during her time as secretary of state.

As Clinton sat on her stool, Trump approached her, and said that, if he won, he would instruct his attorney general to hire a special prosecutor to investigate her conduct.

"There has never been so many lies, so much deception," he said. "There has never been anything like this. ... Lives have been destroyed for doing 1/5th of what you've done, and it's a disgrace."

Clinton, again refusing to be flustered, directed viewers to her website where she said her campaign had fact-checked his false allegations.

"It's just awfully good that someone with the temperament of Donald Trump is not in charge of the law in our country," she said.

"Because you'd be in jail," Trump responded to cheers from the audience.