The presidential debate in Las Vegas began on a frosty note as the candidates once again abandoned the tradition of shaking each other's hands at the outset. And there were moments of serious clashes, including over Trump's history with women, his relationship with Russian President Vladimir Putin and the Republican nominee's immigration positions.
"We have some bad hombres here and we're gonna get them out," Trump said.
But overall, the first 30 minutes of the debate were dominated with exchanges over substantive policy issues harkening back to previous election cycles that lacked the drama and bitter personal battles of 2016. Clinton and Trump had a serious exchange, for instance, about the Supreme Court and gun rights.
Clinton said the court should "stand on the side of the American people, not on the side of powerful corporations and the wealthy."
Trump said that the Supreme Court is "what it is all about" and rebuked liberal Justice Ruth Bader Ginsburg for recent remarks in which she criticized him, before apologizing. He warned that if Clinton was President, she would gut Americans' Second Amendment right to bear arms.
"If my opponent should win this race, which I don't think will happen," Trump said, the Second Amendment will be a "small replica of what we have now."
Clinton denied that she opposes the Second Amendment but called for firearms legislation that included comprehensive background checks, and efforts to close the so-called gunshow loophole.
The candidates also clashed over abortion rights with Clinton insisting she would defend Planned Parenthood and the Supreme Court's Roe v. Wade decision.
"I will defend women's rights to make their own health care decisions," Clinton said, bringing up a previous remark by Trump when he said that women should be punished for getting an abortion.
Trump hit back, saying she would allow late-term abortions.
"You can take the baby and rip the baby out of the womb in the ninth month," Trump said.
Clinton accused Trump of adopting "scare rhetoric" on the issue.
Donald Trump on Wednesday refused to say he would accept the result of next month's presidential election.
"I will look at it at the time," Trump said when challenged during the final presidential debate on his claims that the election is "rigged" against him.
He added: "I will keep you in suspense."
The comments at the Las Vegas showdown marked an extraordinary departure from one of the most fundamental principles of American democracy: the peaceful transfer of power after an election. The remarks were also a dramatic departure from the first hour of the debate, where Trump showed unusual restraint as he and Clinton engaged in substantial policy discussions over issues such as the Supreme Court, the Second Amendment and gun rights.
Hillary Clinton, the Democratic nominee who is leading Trump in most polls, said the Republican nominee's remarks were "horrifying."
"You are not up to doing the job," Clinton charged, claiming that every time events do not turn out in his favor, Trump claimed things were "rigged" against him. She highlighted Trump's past comments lamenting results of the Iowa caucuses, legal judgments against him -- even Trump's complaints when he did not win an Emmy.
Losing his cool
Trump seemed to lose his cool as the debate went on, harshly criticizing Clinton and occasionally getting testy with the debate moderator, Chris Wallace of Fox News. The debate began to take a turn when Trump and Clinton clashed over the Republican nominee's relationship with Russian President Vladimir Putin.
Clinton blasted Trump as a "puppet" of Putin and directly called on him to condemn what she said was a Russian effort to use cyber attacks to influence the election in her opponent's favor.
Trump replied that Putin had no respect for Clinton or President Barack Obama.
"That's because he would rather have a puppet as President of the United States," Clinton said, implying that Putin wanted Trump to win the election.
"No puppet. You are the puppet," Trump said.
Trump said he had never met Putin but allowed that the Russian leader had said nice things about him, and said it would be good if Washington and Moscow worked together to fight ISIS.
But he added: "This is not my best friend."
Clinton and Trump also bitterly sparred over the theme of who is qualified to be President. Wallace pressed Trump on why so many women had come forward to accuse him of sexual assault if the allegations were not true.
Trump said the claims had been "largely debunked."
"I think they want either fame or her campaign did it," Trump said, referring to the women that came forward after he said at the last debate he had never been abusive to any women.
Clinton noted that Trump had implied at several rallies that he could not have made inappropriate advances to the women because they were not sufficiently attractive.
Trump wrongly denied that he had ever made such a remark.
"Donald thinks belittling women makes him bigger. He goes after their dignity and their self worth," Clinton said.
Treatment of women
Clinton said that Trump's treatment of women was part of pattern of behavior that saw him insult a disabled reporter, go after the parents of a fallen Muslim soldier and an American judge of Mexican descent.
She said such tactics were in line with a divisive and very "dangerous vision of our country."
Since the second presidential debate, Trump has faced a string of accusations of sexual assault, all of which he has branded as lies. He also made an accusation that no candidate in modern times has dared to level -- that the election is rigged against him.
The GOP nominee has repeatedly lashed out at House Speaker Paul Ryan, whom he believes is not giving him the support he deserves. As a result, Trump has declared himself "unshackled" and intends to close out his campaign free from an obligation to toe the Republican line.
He's said that Clinton should be forced to take a drug test before their final debate clash, and doubled down on his vow to put her in jail if he is elected.
But Trump can't afford to replicate his performances in the first two debates, when he was diverted from his most potent attacks on trade and the economy, by traps laid by Clinton or her jabs at his personality and business record.
Trump, down eight points in the latest CNN Poll of Polls, is almost out of time to launch what would be one of the most remarkable comebacks of modern times. A new edition of the CNN Electoral Map on Wednesday moved two key swing states, Florida and Nevada, to "lean Democrat." Two states that have voted almost exclusively Republican for decades, Utah and Arizona, are now considered battlegrounds.
CNN called the debate in Clinton's favour 52% to 39%.