To that centuries-old tension the last few decades have added several more. The growth of partisan polarization has increased the potential ideological hostility between the branches, and raised the perceived stakes of presidential elections and high court appointments both.

Meanwhile, the liberal ambitions of the Warren Court and the expanded powers of the Cold War presidency made both branches considerably more imperial relative to both Congress and the states, and neither trend has been substantially reversed. Instead the political abdication of the Congress, the steady atrophy of legislative power and flight from legislative responsibility, means that America is increasingly governed by negotiations between the imperial presidency and whichever philosopher-king has the swing vote on the court.

A dual imperialism is still a separation of power, and a decaying republic with two emperors by definition does not have its Caesar or Augustus yet. Not are we about to get one: Because Trump is too politically weak to win a stark confrontation with the Supreme Court, and Roberts is temperamentally modest and consensus-oriented, their Twitter beef is an illumination of reality, rather than a step into crisis. So there is time for an anti-imperial rebalancing, in which a more assertive Congress somehow brings us back into constitutional equilibrium.