For example, the left has increasingly defined itself as a coalition of progressives and people of color against reactionary Whites. Would that be a viable organizing principle in a world where Republicans win a sizable percentage of non-White votes?

Beyond that, what sort of political positions should the left adopt, if Republicans start to outpoll them? The belief in a frustrated Democratic majority has made the left increasingly critical of the anti-majoritarian features of American democracy. How well will those criticisms read if Democrats take their turn as the party that can’t quite win a popular majority? Might their future selves come to appreciate the filibuster, celebrate the electoral college or regret their endorsement of various court-packing schemes?

Of course, conservatives should engage in similar introspection. If Republicans expected to win more elections, what would they say about the filibuster, or America’s growing preference for running all important decisions through the Supreme Court? For that matter, how would a party swelling with Hispanic and Asian voters position itself on immigration? And if Republicans can assemble a majority of the vote, won’t they want Democrats to accept the legitimacy of that vote? If so, shouldn’t they set a good example now?