Ever since rioters stormed the Capitol on Jan. 6, 2021, the Democratic Party has sought to claim the mantle of democracy, painting Donald J. Trump and his allies as extremists willing to deny the will of voters to cling to power.

Now, after President Biden dropped his re-election bid and Democrats swiftly aligned behind Vice President Kamala Harris as a replacement, Republicans are trying to flip the argument.

In a series of statements and social media posts, Republicans have argued that Democrats, by pressuring Mr. Biden to quit, have “disenfranchised” the 14 million people who voted for him in the party primaries.

The accusation isn’t based on any party rule or supposed legal violation. Instead, it is the Republicans’ latest attempt to muddy the waters on an issue that helped Democrats win key races two years ago. Since Mr. Trump’s attempt to overturn his defeat in 2020, which led to the Jan. 6 riot and criminal charges against the former president, Democrats have cast Republicans as a threat to democratic norms.

They have used images from the Jan. 6 riot in attack ads and mobilized Democratic voters against Republican-backed legislation restricting voting. The issue was especially potent for Democratic governors and secretaries of state in critical swing states, who won every election for statewide office except for governor in Nevada and Georgia in 2022.

On Monday, Mr. Trump tried a new tactic to neutralize that threat, zeroing in on the “stolen” nomination claim. “They stole the race from Biden after he won it in the primaries — A First!” Mr. Trump posted on his social media site. “These people are the real THREAT TO DEMOCRACY!”