During the final presidential debate Wednesday, moderator Chris Wallace asked Donald Trump whether he stood by his recent rhetoric suggesting the election may be “rigged.” Trump waffled, but Wallace asked clearly: Will you accept the legitimacy of the election results?

“I will look at it,” Trump responded. “I’ll keep you in suspense.” He delivered the answer with an impish grin.

“It’s funny,” Clinton said, “but it’s also very troubling.” She then called Trump’s refusal to acknowledge the legitimacy of the election results “horrifying.”

Republicans, of course, have been priming their supporters to expect voter fraud for years. But no major candidate has gone so far as to suggest that he will refuse to accept election results out of a fear that the process was rigged.

Read more Slate coverage of the 2016 campaign.