The reluctance of many GOP candidates to embrace a long-standing tenet of American democracy shows how Trump’s assault on the integrity of U.S. elections has spread far beyond the 2020 presidential race. This year, multiple losing candidates could refuse to accept their defeats.

Trump, who continues to claim without evidence that his loss to Joe Biden in 2020 was rigged, has attacked fellow Republicans who do not agree — making election denialism the price of admission in many GOP primaries. More than half of all Republican nominees for federal and statewide office with powers over election administration have embraced unproven claims that fraud tainted Biden’s win, according to a Washington Post tally.

Acceptance of an electoral outcome — win or lose — was once a virtual certainty in American politics, although there have been exceptions. In 2018, Georgia Democratic gubernatorial nominee Stacey Abrams cited voter suppression as a reason for refusing to concede defeat to Republican opponent Brian Kemp. But unlike Trump, Abrams never sought to overturn the certified result or foment an insurrection.

In competitive races for governor or Senate in Arizona, Florida, Kansas, Michigan, New Hampshire, North Carolina, Pennsylvania and Texas, GOP candidates declined to say that they would accept this year’s…