Republican presidential nominee Donald Trump said, "I'll keep you in suspense," when answering a question about the tradition of accepting the results of presidential elections. (The Washington Post)

Donald Trump’s defiant assault on the presidential election’s integrity reverberated Thursday among his allies and rivals as the GOP campaign and Hillary Clinton’s inner circle argued over how best to face the outcome after the votes are counted.

Trump on Wednesday amplified one of the most explosive charges of his candidacy: that if he loses the election, he might consider the results illegitimate because the process is “rigged.”

Questioned directly as to whether he would accept the outcome should Democratic nominee Clinton prevail Nov. 8, Trump demurred. “I’ll keep you in suspense,” the Republican nominee said. Clinton called Trump’s answer “horrifying,” saying he was “talking down our democracy.”

Trump reiterated the point after flying to Columbus, Ohio, to campaign Thursday, joking, “I would like to promise and pledge to all of my voters and supporters, and to all of the people of the United States, that I will totally accept the results of this great and historic presidential election — if I win.”

He added later, on a more serious note, “Of course I would accept a clear election result, but I would also reserve my right to contest or file a legal challenge in the case of a questionable result, right?”

Highlights of the third presidential debate

At a rally at a downtown Charlotte brewery, one of two to kick off North Carolina’s early voting period, Democratic vice-presidential nominee Tim Kaine said that Trump’s claims of a “rigged” election reminded him of the Third World politicking he had seen as a missionary in Honduras.

“We have a tradition unbroken back to the beginning of this nation,” Kaine said. “He wouldn’t defend our democracy, but he wouldn’t condemn Vladimir Putin’s attempts to tinker with our democracy.”

Kaine also used his speech to criticize the Republican-run North Carolina state legislature for passing a voter ID bill that a federal court later overturned after finding evidence of racial discrimination. There was a difference, said Kaine, between legal efforts to extend voting rights and claims of a “rigged” election.

“If there’s a legitimate concern on Election Day, sure, we’re going to let a court figure it out,” Kaine said.

Kaine said it was important for the Democratic ticket to win by a large margin. “The bigger we can win by, the harder it is for him to whine and have anyone believe him,” he said.

A new Clinton fundraising pitch made the same point Thursday. “We’ve got to beat [Trump] so definitively that Hillary’s victory is undeniable,” read the email to donors. “We need to build up our ground game even more if we want to make that a reality.”

Even as the two campaigns exchanged barbs, President Obama and his wife Michelle hit the campaign trail on Clinton’s behalf. The first lady spoke in Phoenix, a sign that Democrats now see traditionally conservative Arizona as a state they could possibly capture this year.

First lady Michelle Obama delivered a stirring endorsement of “our friend, Hillary” during the campaign rally in Phoenix. She praised men and women from across the country who have written to her in recent days and bemoaned the dark turn the election has taken in recent weeks, blasting Trump’s divisive rhetoric.

“Look at us. Just look at us. We all know better, we all know better. Whether we’re Democrats, Republicans or indpendents, it does not matter,” she said. “We all understand that an attack on any one of us is an attack on all of us. And we know that that is not who we are.”

She called the 2016 election a “crossroads” and said that Clinton’s “powerful” vision of America is backed by “policies to make that vision a reality.”

“Hillary has comprehensive policies to help people. Her opponent has tweets. You decide,” she said.

The first lady also blasted Trump for his suggestion Wednesday night that he may not consider the election results legitimate if he loses.

“You do not keep American democracy in suspense. Because look, too many people have marched and protested and fought and died for this democracy,” she said.

Meanwhile, the president spoke to a rowdy crowd of about 2,800 in Miami. He said Trump’s suggestion that there’s vote rigging “is more than just the usual lie.”

“That is not a joking matter. That is dangerous,” he said. “That undermines our democracy.”

While Clinton and Trump made their distaste for each other clear during their last debate, they will find themselves in the same room again Thursday night at the Al Smith charity dinner at New York’s Waldorf Astoria hotel. The white-tie dinner, which benefits Catholic charities, is a tradition-bound affair featuring comedic speeches by politicians.

Clinton, who arrived in White Plains, N.Y., at 5:30 a.m., has no public events scheduled before then.

Aboard her campaign plane Wednesday night, the Democratic nominee attacked Trump’s refusal to say he would accept the election results. “Our country has been around for 240 years, and we’re a country based on laws, and we have hot, contested elections going back to the very beginning. But one of our hallmarks has always been that we accept the outcomes of our election.”

A handful of GOP senators — including Lindsey O. Graham (S.C.) and Arizona’s Jeff Flake and John McCain — have criticized Trump’s stance.

McCain, who lost to President Obama in 2008, said in a statement: “I didn’t like the outcome of the 2008 election. But I had a duty to concede. A concession isn’t just an act of graciousness. It is an act of respect for the will of the American people, an act that is every American leader’s first responsibility.”

The campaign took yet another unexpected turn Thursday morning when Trump suggested that Clinton had gotten the questions to Wednesday’s debate in advance. “Why didn’t Hillary Clinton announce that she was inappropriately given the debate questions — she secretly used them! Crooked Hillary,” he tweeted.

Many Republicans have questioned the debate process in the wake of a recent WikiLeaks revelation that interim Democratic National Committee chair Donna Brazile may have shared a question in advance of a CNN town hall in March. In an email to Clinton campaign chairman John Podesta, Brazile — a CNN contributor at the time — wrote, “From time to time I get the questions in advance,” and highlighted the issue of the death penalty.

Clinton received a question right along those same lines the next day.

Trump picked up on that theme during his Columbus speech, saying his opponent received “the exact questions to a previous debate, word for word, by Donna Brazile, who is now under tremendous pressure to resign from the DNC, as she should be.”

“That is cheating at the highest level,” he said, as the crowd booed at the mention of Brazile’s name. “But I ask you, why shouldn’t Hillary Clinton resign from the race?”

In an interview with Fox host Megyn Kelly on Wednesday night, Brazile rejected the allegations of improper collusion with the Clinton campaign.

“I am not going to try to validate falsified information,” she said. “I do my homework, I communicate, I talk. CNN has never provided me with questions.”

Some of Trump’s supporters were also circulating a different debate theory on social media Thursday: that the glow emanating from a screen on Clinton’s lectern proved she was learning Fox moderator Chris Wallace’s questions in advance.

The Democratic nominee quickly turned the accusation into a fundraising pitch, retweeting it with the line, “Show Trump his tweets come at a cost — because Hillary supporters are pledging to donate every time he tweets.”

The sparring between the two camps came after the two parties’ candidates got into fiery exchanges over their fitness to serve as president and character traits Wednesday night.

But over the course of the third and final debate, they delved deeper into their substantive differences than they did in the first two forums and offered a clearer contrast in the directions they would take the country. They drew sharp distinctions on the economy, trade, terrorism, immigration and hot-button social issues including abortion and guns.

Russian President Vladimir Putin loomed as an unseen third presence onstage. Clinton and Trump sparred over which of them would be more effective as commander in chief in dealing with his aggression and Russian cyberattacks. Clinton labeled Trump as Putin's “puppet” — prompting Trump to snap back, “You’re the puppet!” — while Trump charged that Putin had “outsmarted and outplayed” her when she was secretary of state.

After Clinton cited the findings of 17 U.S. intelligence agencies that the Russian government had committed espionage — including by hacking Pdesta’s emails — to interfere in the U.S. election, Trump said he did not agree with that conclusion.

“Hillary, you have no idea,” Trump said. “Our country has no idea.”

Rucker reported from Las Vegas. John Wagner contributed to this report from Las Vegas and David Weigel contributed from Charlotte.