-- Rigged or not rigged, that is the question.
"Rigged" has become an exclamation point of sorts in Trump's lexicon, and he uses it regularly in his rallies, in his other speeches and especially on social media to cast doubt about fairness, in many cases when things do not appear to be going his way.
Facing a deficit in the most recent polls in the wake of the release of a tape on which he can be heard bragging about groping women, for which he has since apologized, Trump has doubled down on stoking fears about rigged outcomes in November.
Yet Trump has fought others' claims on the exact same grounds, in one case winning a lawsuit against a pageant contestant who claimed his beauty contest was a fraud.
Here are a few examples of Trump's claims:
After the Colorado caucuses, in which Trump's GOP rival Ted Cruz swept the state's delegates, Trump said that the system was "rigged" against him because he is a political outsider.
PolitiFact said that while there were "plenty of problems with Colorado's caucus system ... there is no evidence the rules were designed to favor a specific candidate."
Regardless, Trump won the party's nomination.
"He would've been a hero," Trump said of Sanders. "But he made a deal with the devil. She's the devil. He made a deal with the devil."
During the second Trump-Clinton debate, on Oct. 9, he repeated the claim, saying that while she lost "fair and square" to Barack Obama in the 2008 primaries, the case was different this time around. "Go back and take a look at those commercials, a race where you lost fair and square, unlike the Bernie Sanders race, where you won, but not fair and square, in my opinion," he said.
Trump laid part of the blame at the feet of former DNC Chairwoman Debbie Wasserman Schultz, who resigned amid a scandal just before the convention after hacked emails revealed that party officials advocated for the defeat of Sanders.
Trump has suggested on more than one occasion that the presidential election may be rigged — a claim that accords with long-held theories about the vote in certain locales but also raised eyebrows among observers.
"First of all, it [the primary season] was rigged, and I'm afraid the election is going to be rigged," Trump said in Columbus, Ohio on Aug. 1. "I have to be honest. Because I think my side was rigged."
"Now we have one left, one left, one left," he said of Clinton. "And in theory, in theory it should be the easiest, but it's a rigged system. It's a totally rigged system. The elections are rigged."
The real estate mogul suggested several times that his supporters should become election "observers" to be on the lookout for voter fraud.
Tuesday in Pennsylvania, Trump made the suggestion to largely white audiences at two rallies — telling a crowd in Ambridge it is "so important that you watch other communities because we don't want this election stolen from us."
Later, in eastern Pennsylvania, he said, "I hear these horror shows. I hear these horror shows, and we have to make sure that this election is not stolen from us and is not taken away from us. And everybody knows what I'm talking about."
The claims, especially about Philadelphia, have been widely panned, and a study by Loyola Law School found that out of the 1 billion votes cast in the U.S. from 2000 to 2014, there were only 31 fraudulent cases, according to The Associated Press.
Experts questioned by ABC News said such fears are largely unfounded.
And some Republicans are telling Trump to cut out the rhetoric.
Clinton Email Scandal
When the FBI decided to recommend no charges against Clinton for her use of a private email server during her time as secretary of state, Trump went on the offensive.
FBI Director James Comey rebuked Clinton for mishandling classified information but stopped short of recommending criminal charges against her in the case.
He said her actions did not rise to the level of criminality because prosecutors would have to prove criminal intent.
"I think she was extremely careless. I think she was negligent. That I could establish. What we can't establish is that she acted with the necessary criminal intent," Comey told a House panel. "'Should have known,' 'must have known,' 'had to know' does not get you there. You have to prove beyond a reasonable doubt that they knew they were engaged in something that was unlawful."
He said the case was reviewed by 20 professionals, all of whom agreed that no charges were warranted.
The Department of Justice reviewed the recommendation and announced that it would not pursue a case against Clinton or her top aides.
"Late this afternoon, I met with FBI Director James Comey and career prosecutors and agents who conducted the investigation of Secretary Hillary Clinton's use of a personal email system during her time as secretary of state," Attorney General Loretta Lynch said in a statement at the time.
"I received and accepted their unanimous recommendation that the thorough, yearlong investigation be closed and that no charges be brought against any individuals within the scope of the investigation."
But Trump suggested that a meeting that occurred between Bill Clinton and Lynch in the days leading up to the decision made a difference, despite Lynch's denying the case was discussed.
Trump has made Hillary Clinton's email scandal a calling card of his campaign, casting doubt on the ability of the FBI to do its job.
"Did you see Hillary Clinton today? She had this little crowd, and they say, 'Oh, it's the biggest crowd.' She had nothing. She had nothing. And they're talking on television because the media's rigged," he told a crowd in Panama City, Florida, on Oct. 11. "Let me tell you."
Trump also said at that rally that reporters for certain news outlets are "just cogs in a corporate political machine."
He has repeatedly assailed the media as dishonest, whipping crowds into a frenzy at stops across the country.
In 2012, Miss USA contestant Sheena Monnin alleged that the contest was a "fraud" because, she said, contestants knew the finalists before they were announced publicly.
Another contestant made the same claim, but Trump, who owned the Miss Universe Organization, which ran the Miss USA contest, sued for defamation.
At the time, Trump called the claims "trashy" and nothing more than "loser's remorse."
Trump ultimately won the suit and $5 million in damages.
In 2012, Trump tweeted that China was "cooking up conspiracy theories that the Olympics are rigged."