If you think impeachment is too political in 2020, remember 1804. That year saw two impeachments, one of which led to a trial of a Supreme Court justice, presided over by a vice president who had just killed a former Treasury secretary in a duel.

Thomas Jefferson was elected in 1800, after a nasty campaign that featured charges of foreign influence and dual allegiances. Jefferson’s first term saw acrimonious political discord—personal attacks on both sides fueled by a hyperpartisan press, one side clamoring to impeach leaders...