Donald Trump and Hillary Clinton answer questions during the third and final debate at the University of Nevada at Las Vegas.

Oct. 19, 2016 Donald Trump and Hillary Clinton answer questions during the third and final debate at the University of Nevada at Las Vegas. Melina Mara/The Washington Post

It was a two-track debate. At times, it was the setting for a detailed argument over serious issues in which Hillary Clinton and Donald Trump offered voters a relatively straightforward clash of progressive and conservative perspectives.

But this is 2016, and eventually the third and final debate on Wednesday reached the fundamental issue of the campaign: whether Trump is fit to be president. Despite her substantial lead in the polls, Clinton did not hang back, as many predicted she would. Instead, she pressed Trump sharply on the entire catalogue of his shortcomings, accusing him of being a “puppet” of Russian President Vladimir Putin and denouncing his treatment of women, his mocking a disabled reporter and his habit of saying that any contest he loses is “rigged” against him.

And she clearly signaled one of the closing themes of her campaign when she declared that Trump had shown “a pattern of divisiveness, of a very dark and . . . dangerous vision for our country.” The election, she said, was about “what kind of country are we going to be.”

Trump drew from his own arsenal of favored attacks on Clinton, from the work of the Clinton Foundation to her use of a private email server and her role in the Obama administration’s foreign policy. “She’s been proven to be a liar,” Trump said.

[Trump’s breathtaking repudiation of American democracy]

Here are key moments from the third and final presidential debate between Democrat Hillary Clinton and Republican Donald Trump, Oct. 19, in Las Vegas. (Sarah Parnass/The Washington Post)

Had the exchanges come down to an ideological fight and simple tit-for-tat, fire and counterfire, it might have constituted a kind of victory for Trump, given his polling deficit and his gaffes and lies in his earlier debate performances. But as the debate wore on, Trump once again left behind moments that will only reinforce the doubts many voters already have about him.

Repeatedly, he refused to disown Putin, and he once again praised him relative to both Clinton and President Obama. “She doesn’t like Putin because Putin has outsmarted her at every step of the way,” he said.

He did himself no good when he accused the nine women who have said he groped and accosted them of being liars, motivated by a desire for fame.

And again and again, when Clinton repeated things that Trump had actually said, he simply denied saying them, providing fact-checkers with another rich Trumpian trove.

From the start, Chris Wallace, the moderator in Las Vegas, tried to press Clinton and Trump on a series of specific issues — what sort of justices they would nominate, how they viewed the Constitution, where they stood on abortion rights and gun control. In each case, they stressed themes congenial to their core constituencies.

Clinton strongly endorsed Roe v. Wade, sharply attacked the Citizens United decision that undercut campaign finance restrictions and stressed that she wanted justices who would stand with ordinary citizens against the wealthy and the powerful.

Trump began with his commitment to the Second Amendment and gun rights and kept coming back to the issue. Although Wallace pressed him repeatedly, Trump refused to say if he wanted Roe overturned, though he predicted that because his Supreme Court appointees would be “pro-life,” Roe would fall. Although Trump no doubt pleased opponents of abortion, Clinton showed passion in the exchange, while Trump seemed to be answering by rote.

[In the third debate, Donald Trump erupts]

Oddly for a campaign in which immigration is a central issue, the third debate was the first in which voters were exposed to an extended look at their sharply different approaches.

But since nothing in this campaign is ever destined to look like the Oxford Union or any other stately discussion of public problems, the first track was overwhelmed by the second. Trump’s obvious purpose was to shake voters away from Clinton. And if Clinton was trying to drive up turnout — her fervor on abortion rights and gun control no doubt helped her with women and liberals — Trump may have been attempting to drive it down, figuring that in a smaller electorate, his committed voters would give him a better chance of prevailing.

Yet Trump suffered from what he always suffers from: an inability to control his anger or stop himself from interrupting, which only reinforced undecided voters’ worst perceptions of him.

The most important moment of the evening was Trump’s refusal to say that if he lost, he would accept the outcome: “I will look at it at the time,” he said. “I will keep you in suspense.”

Never has a candidate for president challenged the legitimacy of the entire electoral enterprise in which he was engaged. Clinton’s core claim is that Trump is a dangerous man who lacks respect for American institutions and American democracy. On this central issue, Trump chose to prove Clinton right.

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