Hillary Clinton glides to victory in the last debate while Donald Trump flails on stage

With less than three weeks to go until Election Day, the third and final presidential debate in Las Vegas was Donald Trump's last chance to change the direction of his plummeting campaign.

He failed. While his performance was somewhat more effective than his showings in the first two contests, he gradually became unwound as the night wore on. Trump did nothing in Wednesday night's debate to narrow the widening gap between him and Hillary Clinton, who won the debate by turning in a steady, consistent performance in Sin City.

The first half hour of the debate was one of the more substantive and civil discussions of all three debates. The candidates fielded questions on the Supreme Court, gun violence and abortion, with Trump maintaining a level of relative calm compared to the meltdown he displayed in the second debate. 

But by the second half, Trump lost his cool, walking into multiple traps Clinton laid for him, be it on Vladimir Putin, immigration, nuclear weapons, his foundation or Syria. He called Clinton "such a nasty woman" and falsely claimed that accusations of sexual assault against him had been debunked. She unveiled a new line of attack on Trump's use of steel from China and undocumented labor in his construction projects, which Trump dutifully confirmed.

Most strikingly, he refused to say he would accept the results of the November election, reiterating baseless assertions of widespread voter fraud and the existence of a conspiracy to elect Clinton, who called Trump's position "horrifying."

It only took a slight provocation for Clinton to lure the real Trump out into the open. Answering a question about immigration, Clinton said Trump "choked" during his meeting with the Mexican president, when Trump did not raise the issue of who would pay for his border wall.

Whatever modicum of self-control Trump exhibited prior to that exchange quickly melted away, and he continually felt the need to defend himself as Clinton went on the offensive. 

Clinton, questioned about what she told bankers behind closed doors in speeches released by Wikileaks, turned the question around to focus on Trump's relationship with Putin, whose government is believed to behind the hack that brought the speeches to light.

Clinton said Putin would rather have a "puppet" in the White House. Trump, who had until then restrained himself from interrupting Clinton, barked in the microphone his response: "You're a puppet."

He went further off the rails from there. He denied having said that he wants more nations to have more nuclear weapons. He fielded a question on the economy — the sole area in which voters trust him over Clinton — and used it to backtrack into an argument over his position on NATO. 

When moderator Chris Wallace raised allegations of sexual assault by multiple women, Trump maintained that the accounts were "fiction," denying that he had questioned the accusers' attractiveness.

But the most frightening response of the evening came when Wallace asked Trump whether he would accept the election results. Trump has been on the campaign trail claiming that the election will be "rigged," an assertion that has no basis in fact.

"Your running mate, Gov. Pence, pledged on Sunday that he and you, his words, will 'absolutely accept the result of this election.' Today, your daughter Ivanka said the same thing," Wallace said. "Do you make the same commitment that you will absolutely, sir, that you will absolutely accept the result of this election?"

"I will look at it at the time. I'm not looking at anything now. I will look at it at the time," Trump said, before claiming that the election was rigged from the beginning since Clinton "should not be allowed to run."

Pressed by Wallace, Trump said he would "keep you in suspense."

Clinton rightly pointed out that such a position flies in the face of years of American political tradition.

"That is not the way our democracy works," she said. "We've been around for 240 years. We've had free and fair elections. We've accepted the outcomes when we may not have liked them, and that is what must be expected of anyone standing on a debate stage during a general election."

"I, for one, am appalled that someone who is a nominee of one of our major parties would take that position," Clinton continued.

The debate ended with several questions about foreign policy that Trump stumbled through, time ticking away with him failing to land a blow to change the direction of the race.

Clinton enjoys a huge lead in the polls with the election just 19 days away, a gap that has never been overcome in modern history. The final debate was Trump's last best shot to reverse his political fortunes and arrest his decline. Instead, he turned in a performance that will do little to prevent a Clinton landslide on Election Day.