Donald TrumpDonald John TrumpLieu: There will be 'widespread civil unrest' if Trump fires Mueller Attorneys for Trump, Mueller hold face-to-face meeting to discuss potential interview topics: report Trump tariffs not helpful for nuclear talks, South Korea says MORE opened up a Thursday campaign rally by saying he'll accept the results of the presidential election as long as he wins.

"I will totally accept the result of this great and historic presidential election," Trump told supporters in Delaware, Ohio. 

He then paused dramatically. 

"If I win."

The crowd went wild.

Later in the speech, Trump said that he would accept a "clear election result," leaving the door open to conceding the race if Hillary ClintonHillary Diane Rodham ClintonTrump adds to legal team after attacks on Mueller Press: You can’t believe a word he says Feehery: March Madness MORE wins by an overwhelming margin.

"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," Trump told his crowd. 

"And always, I will follow and abide by all of the rules and traditions of all of the many candidates who have come before me." 

"Bottom line," he added to cheers, "we are going to win."

The Republican nominee has faced a backlash for declining to say at Wednesday's night's debate that he would accept the results of the election. He said he would keep the country in “suspense.”  

As Trump falls in the polls, he has taken to telling supporters that the media and widespread voter fraud are "rigging" the election against him.

At Thursday's rally, Trump said the only reason he won't accept the results in advance is because he's convinced Clinton is cheating.

"We want fairness in the election," he said. "Don't be naive folks."

"A campaign like Clinton's that will incite violence is truly a campaign that will do anything to win," he said.

The Republican said Clinton is the most corrupt and dishonest person ever to run for president.

"It was in that context that I was asked, in advance, to concede the results on election night, if for some reason we should lose," he said, referring to the debate. "That was sort of an unprecedented question."

Trump said that if Democratic nominee Al GoreAlbert (Al) Arnold GoreKim Jong Un’s killer Trump trap Cuomo: 'Offshore drilling is a really, really dumb idea' Left-wing, right-wing: The case for realignment of political labels MORE or Republican nominee for president, George W. Bush, had agreed to the same question three weeks before the 2000 election, there would have been no Supreme Court case contesting the recount in Florida. 

"In effect I'm being asked to wave centuries of legal precedent," Trump said, "designed to protect the voters."

That argument isn't sitting well with some Republicans.

Sen. John McCainJohn Sidney McCainTrump informally offered Cohn CIA job before changing his mind: report Schiff: I thought more Republicans would speak out against Trump Trump presses GOP to change Senate rules MORE (R-Ariz.), who withdrew support from Trump earlier this month, issued a lengthy statement Thursday saying the loser of the election has a “duty to concede” the race.

Recalling his own "reluctant" concession of the 2008 race to President Obama, McCain said accepting the results "isn’t just an exercise in graciousness."

"It is an act of respect for the will of the American people, a respect that is every American leader’s first responsibility. ... This election must not be any different." 

It seems unlikely that such statements will convince Trump to change his rhetoric.

Returning to the argument that the race is rigged in Clinton's favor, Trump pointed to emails released by WikiLeaks that suggested that Democratic National Committee interim chair Donna Brazile shared a CNN town hall question with the Clinton campaign in advance during the Democratic primaries. Brazile has denied sharing a question with the campaign.

"She should resign," Trump said of Brazile. "How can a woman do that? That is cheating at the highest level." 

"But I ask you, why shouldn't Hillary Clinton resign from the race?" he continued. "She was given these questions. She used these questions, studied these questions, got the perfect answer for the questions. 

"That is very dishonest," he added. "This is even bigger because we are going for the presidency of the United States."

Trump joked that if it were discovered that he received questions in advance "they would call for the re-establishment of the electric chair." 

- Updated at 1:26 p.m.