President Trump’s decision to fire 46 United States prosecutors may yet go down as his finest hour. He hasn’t explained the timing. In and of itself it’s not unusual for an incoming administration to ask for the resignations of the U.S. attorneys of the previous regime. Mr. Trump’s action, though, comes amid a broad campaign among his political adversaries to nullify the vote in November. The president may simply have concluded that the country needs to be fully confident that prosecutors are free of political hostility.

Certainly the degree to which the so-called “deep state” has sought to suborn Mr. Trump’s presidency is astonishing. We haven’t seen anything like it in all our years of newspapering. That campaign is being conducted via leaks to a press that itself has become highly politicized. In recent weeks, though, we’ve started to see the readying of what looks like a campaign of litigation to tie up the new presidency in court. States piling on against the presidential orders in respect of refugees appear to be the least of it.

On Tuesday, several liberal organizations wrote to the United States attorney for Manhattan, Preet Bharara, asking him to investigate the Trump Organization over foreign emoluments. The New York Times chimed in with an editorial in this morning’s paper urging Americans to — as its headline put it — “sue while the conflicts are hot,” that is to pile onto the administration with litigation. The refusal by Mr. Bharara to resign (he was then fired) will stoke worries that he was preparing a political probe of the president.

Particularly because the president’s power to dismiss officers of the executive branch is so well established in constitutional law. It had been challenged in 1867, when Congress passed the Tenure in Office Act. It required President Andrew Johnson to get the consent of the Senate before firing any official who’d been elevated to office with the advice and consent of the Senate in the first place. The House impeached Johnson for firing Secretary of War Stanton, but the Senate acquitted the president. Stanton slunk off in disgrace.

In 1887, Congress repealed the Tenure in Office Act altogether. Yet in 1926, a postmaster at Portland, Oregon, Frank Meyers, tried to hang onto his job after having been dismissed. The Supreme Court scotched Myers’s scheme. Its opinion was written by Chief Justice Taft, the only former president to have served on the Supreme Court. As if to make sure that there would be no misunderstanding, the Supreme Court ruled the Tenure in Office Act unconstitutional — 39 years after it had been repealed.

In any event, rarely in our history has the logic of the president having authority over federal prosecutors and other officers seemed so clear. Thirty of the 50 states voted for Mr. Trump for president. He may not have won the popular vote (had the system been designed around the popular vote, Mr. Trump might have campaigned in the high population states). His constitutional mandate is clear. Mr. Trump, the states, and the voters deserve to have an administration led by officers prepared to spring to on the mandate won at the polls.