WASHINGTON (AP) — Threatening to upend a fundamental pillar of American democracy, Donald Trump refused to say he will accept the results of next month’s election if he loses to Hillary Clinton. The Democratic nominee declared Trump’s resistance “horrifying.”

Trump had spent the days leading up to Wednesday’s presidential debate warning voters that the election would be “rigged.” Asked whether he would accept the outcome if Clinton emerges victorious, he said: “I will tell you at the time. I’ll keep you in suspense.”

Some Republicans recoiled at Trump’s startling statement. South Carolina Sen. Lindsey Graham said his party’s nominee was doing the country a “great disservice” by suggesting the election is rigged and Arizona Sen. Jeff Flake called Trump’s comments “beyond the pale.”