When Donald Trump’s campaign was accused of spreading “fake news,” he quickly appropriated the term for himself. The true purveyors of fake news, he claimed, were television networks like CNN and newspapers like this one.

Now, as Mr. Trump and his allies seem on the verge of staging a coup against independent institutions and the rule of law — maligning the special counsel Robert Mueller and threatening a purge at the F.B.I. — the president’s supporters are appropriating yet another word for themselves. Mr. Mueller’s investigation aims to “destroy” the Trump presidency “for partisan political purposes and to disenfranchise millions of American voters,” the Fox News host Jesse Watters claimed on Saturday. “We have a coup on our hands in America.”

This marks a new era in American politics. The Republican Party is no longer just obfuscating the truth or defending the president when he is accused of wrongdoing. Rather, Mr. Trump, Fox News and Republicans in Congress seem to be actively using falsehoods to prepare an assault on the institutions that allow American democracy to function.

In all democracies, politicians occasionally lie to cover up scandals or exaggerate their legislative accomplishments. In the United States, the rise of the right-wing news media in recent decades has tempted politicians to play to their own supporters without worrying whether their rhetoric is inflammatory or fair. But the construction of an alternate reality that obviates the very possibility of conducting politics on the basis of truth is a novelty in this country. And it is increasingly becoming obvious that it will serve a clear purpose: to prepare the ground for egregious violations of basic democratic norms.