Generally, Donald Trump’s Twitter beefs are an expense of spirit and a waste of breath. But a minority of them are genuinely edifying, and illustrations of his likely world-historical role — which is not to personally bring down our constitutional republic, but to reveal truths about our political situation, through his crudeness and goading of others, that might be harbingers of the Republic’s eventual end.

Last week’s beef with Chief Justice John Roberts was such a case. After the president complained that an “Obama judge” from the 9th Circuit had ruled against his administration’s asylum policy, the chief justice issued a highly unusual rebuke, declaring that “we do not have Obama judges or Trump judges, Bush judges or Clinton judges,” and an “independent judiciary is something we should all be thankful for.” This predictably inspired a tweeted rejoinder from the president: “Sorry Chief Justice John Roberts, but you do indeed have ‘Obama judges,’” Trump began, before dilating on his grievances against the 9th Circuit’s alleged overreach.

The Official Washington response to this beef was to accuse Trump of once again degrading important constitutional norms — which in a sense his attack on the idea that judges’ legitimacy transcends the partisan origins of their appointments obviously did.

But to anyone who lived through the Merrick Garland and Brett Kavanaugh nominations, the idea that this norm would be resilient absent Trump’s Twitter provocations seems laughable. What was once a conservative assumption dismissed as extremism by the bien-pensants — that the Supreme Court is a highly ideological institution defined by partisan bias and anti-democratic overreach — is now a commonplace liberal belief as well.

That truth reflects an old problem joined to several new ones. The old problem is that the Supreme Court’s legal supremacy over the White House depends upon the presidency’s willingness to accept the court’s rulings. From Andrew Jackson’s conflict with John Marshall over Cherokee removal to Abraham Lincoln’s suspension of habeas corpus to Franklin Roosevelt’s attempts to force the court to accept the New Deal, there have always been tensions in the American republic between judicial authority and presidential power.

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.

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.

But if Congress prefers abdication, a two-emperor system isn’t built to last. Come a crisis, one must be master, the other must submit. That’s the important message of Trump v. Roberts. Let those with ears, hear.