Contra @JonathanTurley the primary purpose of impeachment is *not* removal, though that is an important punishment. More important purposes are, per Hamilton to provide "a method of NATIONAL INQUEST into the conduct of public men"

Franklin: "to provide in the Constitution for the regular punishment of the Executive when his misconduct should deserve it, and for his honorable acquittal when he should be unjustly accused."

It is to impose “political punishments” for “political crimes and misdemeanors" not “ within the sphere of ordinary jurisprudence. [but which are] founded on different principles; are governed by different maxims; and are directed to different objects.” James Wilson

Madison: Impeachment shall be used for "defending the community against incapacity, negligence, or perfidy."

Hamilton, again, impeachment serves to provide "a bridle in the hands of the legislative body upon the executive servants of the government." What is the meaning of that bridle if the executive servants can escape punishment by resigning or whenever they are late in their term?

Good lawyers can argue both sides of many questions, but the argument that the impeachment power extends only to current officials defies logic, text, history, original meaning, and more.

To those who argue that there's little explicit commentary from the Founders on impeachment of former officeholders -- that's because *it was obvious* to them that the impeachment power extended to former officeholders.

The most famous contemporaneous impeachment in England was of the *former* British governor of India, Hastings, which was prosecuted by the intellectual godfather of Anglo-American conservatism, Edmund Burke.