1. An impeachable offense is anything Congress says it is.

People pushing for President Obama’s impeachment have cited rationales ranging from the border crisis to Benghazi to Obamacare to the dismantling of “our constitutional republic, our national security, our electoral system, our economic strength, our rights and liberties.” In other words, anything goes. This echoes the characterization by Gerald Ford, who as House minority leader in 1970 made the ill-considered statement that “an impeachable offense is whatever a majority of the House of Representatives considers it to be at a given moment in history.” (This interpretation was, not surprisingly, part of a frivolous effort to impeach Supreme Court Justice William O. Douglas, whom Ford denounced for espousing “liberal opinions,” for defending the “filthy” Swedish film “I Am Curious (Yellow)” and for writing a magazine article that “praises the lusty, lurid, and risque along with the social protest of left-wing folk singers.”)

But Congress’s exclusive power to impeach does not license it to abuse that power, any more than the Supreme Court’s final say on laws gives it license to deliver arbitrary rulings. The framers carefully defined the grounds for impeachment as “treason, bribery, or other high crimes and misdemeanors” — language with British legal precedent. They clearly did not want removal of the president subject to congressional whim. Indeed, they rejected the addition of “maladministration” after James Madison cautioned that “so vague a term will be equivalent to a tenure during pleasure of the Senate.”