Whether Donald Trump succeeds in making America great again will ultimately be sorted out by historians. But even amid the wild protests, the Trump presidency may already be nudging blue-state America in healthy directions.

Who could have predicted, for example, that it would be Democrats warning the U.S. not to be naive about Russia? Or the Obama team instructing Republicans on the virtues of global trade agreements? Or progressives making the case for states’ rights, especially on immigration?

Much of this, of course, is situational ethics: A defeated Democratic Party is where it is on many issues largely out of simple opposition to Mr. Trump. Even so, there’s an opportunity for a blue-state rediscovery of federalism, and it ought not be mocked.

At the unserious level, the rediscovery manifests itself in the absurd, such as the call for California to secede from the United States as Britain voted to leave the European Union. The more serious rediscovery begins with an appreciation that federalism does not necessarily mean conservatism. It might just as well mean carving out political space for blue-state models and mores.

Over at the New Republic, Kevin Baker chimes in with a piece entitled “Bluexit: A Modest Proposal for Separating Blue States from Red.” Mr. Baker starts from the idea that blue states, which send more dollars to Washington than they receive in return, are subsidizing red ones. Federalism, he says, is a way for blue states to boot their “crazy, deadbeat in-laws out of the house”—and show America what they can do.