The Trump administration dropped a political bombshell late Friday as all 46 holdover United States attorneys were ordered to immediately resign — including New York’s political-corruption-busting crusader, Preet Bharara.

Big mistake.

The resignation order itself isn’t unusual: US attorneys serve at the president’s pleasure and most previous presidents have done the same upon taking office.

What’s stunning is that Bharara was included in the order. After all, both then-President-elect Trump and Attorney General-designate Jeff Sessions last November specifically asked him to stay on the job, and he agreed.

Yet Friday, when asked if there were any exceptions to the order, a Justice Department spokesman said: “Everyone gone.”

Trump and Sessions were right the first time, and they need to rescind the order for Bharara, the most successful prosecutor yet when it comes to undoing New York’s culture of political corruption.

Indeed, this comes as he’s still investigating the de Blasio administration and other key figures in New York for possible corruption. It’s absolutely the wrong time for him to leave.