President Donald Trump’s rejection of an orderly transfer of power to Joe Biden, accompanied now by his refusal to concede defeat based on fabricated allegations of electoral fraud, poses a profound threat to American democracy—the most profound yet of his dangerous presidency. That the Republican leadership has supported him in his subversion severely worsens the situation, with dire implications for the future of American politics.

It is unprecedented for an unsuccessful incumbent President and his leading congressional allies to refuse to acknowledge the results of an election. Since 1800-01—the first time the country experienced anything like a transfer of power from one party to another—defeated presidents have bowed to the will of the people. They have not always done so happily. After his loss in 1800, John Adams wrote bitterly that “we have no Americans in America,” and that “a group of foreign liars, encouraged by a few ambitious native gentlemen have discomfited the education, the talents, the virtues, and the property of the country.” Adams was so disgusted that he refused to attend the inauguration of his successor, Thomas Jefferson. But Adams accepted that, as he wrote, “we federalists” had been “completely and totally routed and defeated.”

In 1828, Adams’s son, John Quincy Adams, was depressed by his loss to Andrew Jackson after a savage campaign on both sides, although he had foreseen the outcome for some time. Like his father, Adams failed to show up for his successor’s inauguration, and a few years later protested when the Harvard Board of Overseers voted to present President Jackson with an honorary degree. (Himself a member of the Board, Adams boycotted that ceremony as well, dejected that “my darling Harvard” would honor “a barbarian who could hardly spell his own name.”) In 1869, the impeached and discredited Andrew Johnson, having been passed over for re-nomination, skipped the inauguration of Ulysses S. Grant.

But personal bitterness is one thing; disloyalty to democracy another. Until now, no defeated President has failed to respect the transfer of power, let alone deny the results of the election. There have been two hotly disputed elections, in 1876 and 2000, which produced prolonged wrangling over who won. But even then, once the winner was determined, the loser—first Samuel Tilden, then Al Gore—gave way.