LAS VEGAS — Throughout the long and tawdry presidential campaign, both Donald Trump, by dint of his personality, and Democrats, by dint of the damage they see him doing to his cause, have kept the attention focused on him.

On Wednesday, from a stage at the University of Nevada, Las Vegas, Trump will face an imperative that sounds simple but has eluded him for months: to turn a fierce spotlight onto his Democratic opponent, Hillary Clinton.

"This election has been about Donald Trump from Day One; that's the only context he has," said Democratic pollster Peter D. Hart. "You look at this as his last, best chance. If he continues to do the same things he's always done, the results are going to be the same."

If Trump can manage to shift attention to his opponent, he has material to work with. Clinton enters the third and final presidential debate with a persistent lead of at least middling single digits in almost all national polls and a strong hold on states Trump needs to win, but she faces challenges of her own.

She has been buffeted in recent days by the release of hacked emails, which have renewed questions about her tenure as secretary of state. That offers Trump an opening, if one less sizable than the difficulties that have enveloped him since the last debate 10 days ago. But benefiting will require a deftness and discipline that Trump has been unable or unwilling to maintain in the two previous debates.

This final debate occurs under extraordinary conditions.

Trump, accused by more than a dozen women of varieties of sexual assault, asserts that Clinton is part of a global conspiracy to undermine U.S. independence. Clinton returns the sentiment by contending that Trump lacks the temperament to be trusted with the nation's nuclear weapons and is being aided by hackers directed by the Kremlin.

The way they've pushed those arguments has not helped Trump gain ground.

Clinton has deflected some of the sharpest assaults on Trump to her surrogates, in what appears to be an effort to alienate as few voters as possible. First lady Michelle Obama laid into the Republican nominee last week as representing a destructive anti-woman worldview. President Barack Obama on Tuesday belittled Trump as "whining" about his loss rather than being a stand-up leader.

But Trump is the dominant personality in his campaign by far, and so he has taken on the largest role in reminding voters of Clinton's failings. He has done so in biting and mocking ways that have served to reinforce Clinton's criticisms of him.

"It's like a boxer with a glass jaw leading with their chin," said Republican pollster Ed Goeas. "When he is the one leading the fight … he not only stirs up her negatives, but his own negatives."

Still, for all the drama that has marked the presidential contest, the race for the White House has been remarkably stable. And that stability, in defiance of all the tumult, makes it harder for Trump to overcome Clinton's lead.

Clinton and Trump started the campaign with high unfavorable ratings; now, less than three weeks before Election Day, those numbers have barely budged.

Asked last October if they were optimistic or pessimistic about Trump's candidacy, 67 percent of Americans told the NBC News/Wall Street Journal pollsters they were pessimistic. This month, that number sat at 65 percent. Asked about Clinton's candidacy, 56 percent said they were pessimistic a year ago; this month that figure was 55 percent.

That stasis, after all the campaign's furor, speaks to an electorate that is resistant to moving sharply toward one or the other's campaign.

"People sized them up pretty early and haven't changed their opinions very much," said Hart, whose firm co-directs the NBC News/Wall Street Journal polls with Republican pollster Bill McInturff.

Overall, an average of polls conducted by Real Clear Politics finds Clinton ahead of Trump by almost 7 percentage points nationally.

More sobering for Trump was his performance in the states whose electoral votes will tip one of the candidates into the White House. In those states, Trump had a substantial lead only in Iowa, where he was ahead by an average of less than 4 points. Clinton was ahead by at least that amount in Florida, New Hampshire and Nevada, and by almost that much in North Carolina.

Trump was far behind in states he once wanted to contest, like Pennsylvania, Virginia and Colorado. The race was a dead heat in Ohio, the state every winning Republican nominee has claimed.

Perhaps most fearfully for Trump, he led by a mere 1 point in Arizona, typically a Republican state. Other polls showed weakness in two other loyal GOP states, Georgia and Texas.

The reason for Trump's difficulties is the teeter-totter he has ridden since the beginning of his campaign.

His opposition to trade deals, anger at immigration policies and expressions of cultural affinity with blue-collar whites secured his hold on that slice of the electorate. But those arguments have repelled suburban, college-educated voters, an increasingly large part of the voting population and one that typically has sided with Republicans.

Trump has done almost nothing in recent weeks to try to solve that problem. He has publicly criticized the nation's highest-ranking Republican, House Speaker Paul D. Ryan, and other GOP figures. After slicing Clinton for being critical of women who allege sexual misconduct by her husband, Bill, he flayed women who made the same accusations against him.

He suggested that Clinton had been on drugs during their second debate — one that voters said she had won. In West Palm Beach, Fla., on Friday, he used conspiratorial language to question her patriotism, asserting that she was meeting "in secret with international banks to plot the destruction of U.S. sovereignty."

Perhaps most notable has been Trump's assault on a main tenet of American democracy — that fair elections usher in a peaceful exchange of power. His insistence that the electoral system is rigged and that voters in nonwhite areas cast illegitimate ballots has prompted bipartisan rebukes.

In Colorado on Tuesday, he insisted that he was correct in saying that heavily nonwhite inner cities were rife with instances of voting fraud, even though there is no evidence to back up his claim.

"If you talk about them, they say bad things about you," he said. "They call you a racist."

Clinton, content to give Trump the attention, had no public events Tuesday; for days she has focused on debate preparation. A senior campaign aide, Jennifer Palmieri, said Clinton was ready for whatever Trump might say in an effort to pull ahead.

"If he chooses to continue to embrace his strategy of a scorched-earth campaign and bringing that to the debate stage, she'll be prepared to handle that," Palmieri told reporters, "as she has the last two times."