Yet the pattern isn’t inevitable, and it’s crucial to see that the very closeness of elections blinds politicians to potential ways of breaking out of it. As the political scientist Frances Lee has shown, the minority party in Congress now always thinks it’s one election away from power and so sees no reason to change its appeal or to bargain to address the country’s longer-term needs. Younger politicians who have known only this period assume there is no other way — that short-termism is unavoidable and governing means frantically expending rather than patiently amassing political capital.

This also intensifies party cohesion. As the political scientist Daniel DiSalvo has argued, internal factions let parties evolve toward new voters and vice versa, but our era has seen fewer and weaker factions. Narrow elections invite strict unity, so the parties now hunt heretics rather than seek converts. Witness, for instance, the Arizona Republican and Democratic Parties censuring Gov. Doug Ducey and Senator Kyrsten Sinema for undermining party unity. Both parties act as if they have too many voters, rather than too few.

Breaking this pattern would have to start by acknowledging a truism: Bigger majorities are possible if politicians seek broader support. That sounds obvious, yet it has eluded our leaders for a generation because it requires seeing beyond our age of deadlock.