President Trump has now made obvious his contempt for the notion that Congress has any authority to hold him accountable. He has signaled that he won’t mount any defense to impeachment charges in the House over his scheming in Ukraine, insisting it is somehow beneath him to participate in a constitutional process.

If Mr. Trump is so clear in his own mind that he didn’t try to pressure the Ukrainian government to interfere in the 2020 election, why won’t he send the secretary of state, Mike Pompeo, to testify under oath that there was no quid pro quo? Instead, he has issued a blanket refusal to allow officials of his administration to testify or submit documents demanded by Congress. His approach is pitting Republican House members’ fealty to him against their respect for their own institution. They are making a fateful choice to diminish the House.

At an earlier time, such monarchical behavior from a president would have been met with bipartisan insistence on accountability to Congress and thus to the American people. With the power of the purse and a shared moral seriousness, a bipartisan majority in Congress would have brought the administration to its senses, if not to its knees, in a day. In any event, no previous president has taken the risk of provoking such congressional wrath. Richard Nixon was far more compliant with Congress, as was Bill Clinton. They felt like they had to be. And they felt like they should be. Those were different eras.

No doubt, Republicans fought tooth and nail to defend President Nixon during the Watergate scandal, as Democrats later fought to defend President Clinton during his impeachment in the Lewinsky affair. But in those previous eras members of Congress of both parties also recognized the gravity of their responsibility and brought far more open minds, not just their partisan identities, to bear on the evidence. Today’s Republican legislators have supported President Trump’s rejection of Congress’s independent authority by showing nothing but indifference to the alarming testimony of credible witnesses, and scorn for public servants who have had the courage to testify — an attitude that should be infuriating to anyone who expects legislators to honor their oath of office.