DELAWARE, Ohio — Donald Trump said Thursday that he would accept November's election results — so long as he's the winner.

The GOP nominee doubled down on controversial and unprecedented claims that he may not accept the results on November 8, first made at the third and final presidential debate Wednesday.

Warning of a "major announcement," Trump led off his first public appearance since the debate with the "promise and pledge" to his supporters: "I will totally accept the results of this great and historic presidential election — if I win." The brief pause and defiant words that came after it immediately incited cheers from the crowd.

Related: GOP Slams Trump: Not Accepting Election Results Would Be 'Beyond the Pale'

Despite his initially obstinate comment, Trump's argument softened somewhat as he went deeper into his remarks. He called it "unprecedented" to have to concede results before they're known — a belief Trump hasn't had to be asked about before because it is a basic and fundamental principle of American democracy. But as Trump sees it, not committing means allowing himself the ability to legally contest a close election.

"I will accept a clear election result," Trump allowed. "But I would also reserve my right to contest or file a legal challenge in the case of a questionable result." He cited the landmark 2000 Supreme Court case Bush v. Gore as precedent for needing to contest an election.

Prior to Trump's speech, Republican National Committee Communications Director Sean Spicer told Fox News Radio he would like Trump to clarify his remarks on not accepting election results. Spicer noted, however, "I don't think Donald Trump walks back anything."