Donald Trump promised on Thursday to accept the outcome of the election — if he wins.

The declaration came just hours after he stirred up the final presidential debate by leaving open the possibility he may challenge the results.

"Ladies and gentleman, I want to make a major announcement today," he said at a rally at the Delaware County Fair in Ohio. "I would like to promise and pledge to all of my voters and supporters and to all of the people of the United States that I will totally accept the results of this great and historic presidential election if I win."

When asked at Wednesday night's debate whether he would "absolutely accept" the results of the election, regardless of the outcome, Trump responded: "What I'm saying is that I will tell you at the time. I'll keep you in suspense."

On Thursday, Trump elaborated by saying: "This is having nothing to do with me, but having to do with the future of our country. We have to have fairness."

"Of course 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," he said. "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. Always."

The Republican nominee also renewed an accusation he made earlier in the day that Hillary Clinton "inappropriately" received debate questions ahead of time.

@realDonaldTrump: Why didn't Hillary Clinton announce that she was inappropriately given the debate questions - she secretly used them! Crooked Hillary.

On Thursday morning, Trump campaign manager Kellyanne Conway told CNBC that it would be "insane" to concede an election that had not been held yet.

Sen. Barbara Boxer , D-Calif., responded quickly on Twitter to Trump's Ohio remarks.

Only a dictator would say he will accept the election results on one condition – if he wins.

— CNBC's Everett Rosenfeld and Matthew J. Belvedere contributed to this report.

