The question of impeaching Donald Trump is about replacing the toxic partisanship of today’s Republican party with America’s traditional rule of law. It has become a constitutional imperative.

Since Richard Nixon, Republican presidents have pushed the envelope of acceptable behavior under the guise of patriotism, and Democrats have permitted their encroaching lawlessness on the grounds of civility, constantly convincing themselves that Republicans have reached a limit beyond which they won’t go. Each time they’ve been proven wrong.

Nixon resigned in 1974 because his attempts to cover up his involvement in the Watergate burglary made his obstruction of justice clear. Republican leaders warned Nixon that if the House of Representatives impeached him, the Senate would convict. Republican congressmen of the time believed in the rule of law.

Gerald Ford’s subsequent pardon of Nixon was perhaps given in that spirit: when the law rules, it permits mercy. But the absence of a humiliating public exposure of Nixon’s participation in Watergate, and the lack of a permanent bipartisan condemnation, gave Nixon loyalists cover to argue that he wasn’t guilty of crimes. Instead they claimed Nixon had been hounded out of office by outlandish liberals determined to undermine him and the country.

Ever since, Republican extremists have employed this rhetoric whenever they break the law or erode constitutional norms.