In October, Michael Gerson recognized that Trump was trying to talk Republicans into “mental secession.” If anything, he was too optimistic: The mental secessions had already occurred, among Republicans and Democrats alike. We live and govern ourselves less as a single nation than as two rival nations on contested lands. At any given moment, one nation is in power, while the other spends four years enduring it, resisting it, and looking forward to regime change.

Mental secession results from the way we live. We increasingly segregate ourselves geographically into communities of shared values, as Bill Bishop documented a decade ago in The Big Sort. And we segregate ourselves intellectually, relying heavily on politically or culturally inbred sources of information. No wonder a presidential election’s losing side sees the winners like foreign occupiers—the two sides live in different worlds.

Mental secession is worsened by the way we govern ourselves. Our Constitution originally entrusted lawmaking to Congress, so that our laws would be enacted through a checked-and-balanced process of deliberation and compromise, sometimes over the course of years or decades. Today, however, our government’s center of gravity is the administrative state, which makes law much more swiftly and unilaterally, and thus less moderately; groups not part of the president’s political coalition have no substantial voice in governance, except when they sue to block the agencies’ work.