WASHINGTON ― Donald Trump is not about to accept the outcome of this election.

Casting doubt on the very essence of our democratic system, Trump made his boldest the-election-is-rigged claim Wednesday night during the third and final presidential debate, refusing to commit to accepting the outcome of the race and claiming that Hillary Clinton shouldn’t even be allowed to a run ― claims that Clinton called “horrifying.”

“I will look at it at the time,” Trump said when asked whether he would accept the results. When debate moderator Chris Wallace pressed him on the issue, he said, “I’ll keep you in suspense.”

“If you look at your voter rolls, you will see millions of people who are registered to vote” who shouldn’t be registered, Trump said. He added that not only was there widespread corruption, but that Clinton “should not be allowed to run.”

“It is crooked,” he said. “She is guilty of a very, very serious crime. She should not be allowed to run, and just in that respect, I say it is rigged.”

Trump was referring to Clinton’s email scandal, a subject he often hits. But Wednesday night was Trump’s most direct refusal to accept the results of the Nov. 8 election.

It was, as Clinton summed it up, “horrifying.”

“Every time Donald thinks things are not going in his direction, he claims whatever it is, it is rigged against him,” Clinton said. “The FBI conducted a yearlong investigation into my emails that concluded there was no case.”

Clinton brought up that when the FBI said there was no case, Trump said the FBI was rigged. When he lost the Iowa caucus, he said that was rigged. When he lost the Wisconsin primary, he said that was rigged, too. When he got sued over fraud for Trump University, the court system was rigged. “There was even a time when he didn’t get an Emmy for his TV program three years in a row, and he started tweeting that the Emmys were rigged,” Clinton said.

“I should’ve gotten it,” Trump responded.

Clinton continued that this was how Trump thinks. “And it’s funny, but it’s also really troubling,” Clinton said. “That is not the way our democracy works. We’ve been around for 240 years, we’ve had free and fair elections, we’ve accepted the outcomes when we may not have liked them, and that is what must be expected of anyone standing on a debate stage during a general election.”

“Let’s be clear about what he is saying, and what that means. He is denigrating, he is talking down our democracy, and I, for one, am appalled that somebody who is the nominee for one of our two major parties would take that position,” she said.

Trump’s claims of widespread voter fraud played into a long-running myth that has been played up by Republican officials and the conservative media in recent years.

Still, as moderator Chris Wallace noted Wednesday night, Trump’s vice presidential nominee Mike Pence said the campaign would accept whatever outcome came. And Trump’s campaign manager, Kellyanne Conway, said on CNN after the debate that they would accept the outcome.

But that wasn’t Trump’s position.

In recent weeks, Trump has taken to proclaiming that the election is rigged. What that means is unclear, probably on purpose.

At times, Trump has seemed to mean just that the media has colluded against him. On Wednesday night, he said the media was “so dishonest and so corrupt.” At other moments, “rigged” seems to mean our election is susceptible to wide-spread voter fraud.

While the first claim is difficult to prove either way ― what does collusion in this context even mean? ― the latter claim is demonstrably false. These elections are governed by states and local governments. Both parties have election watchers to point out and contest irregularities. Voting machines are tested in public with witnesses from both parties watching. There are backstops in place to check election results long after polls have closed.

To “rig” an election, it would take cooperation from multiple local officials, of both parties, in multiple counties, to affect just one state. And it would only take one whistleblower to blow up the plan.

In 14 years of elections, with more than 1 billion ballots cast, an investigation into voter fraud found just 31 cases of in-person fraud.

Still, Trump now raising questions about Clinton’s right to run for president is his most direct assault over the “rigged” election to date, and represents his most aggressive stance yet.

Editor’s note: Donald Trump regularly incites political violence and is a serial liar, rampant xenophobe, racist, misogynist and birther who has repeatedly pledged to ban all Muslims — 1.6 billion members of an entire religion — from entering the U.S.