But this demographic divide goes deeper. As Paul Taylor shows in his seminal book “The Next America,” we are “increasingly sorted into think-alike communities” defined by ethnicity, education, and economic status. And so geography mirrors demography.

Clinton’s 3 million-vote edge came from but 420 of our 3,100 counties. The space between is best measured by economics. The 16 percent of counties supporting Clinton accounted for 65 percent of our GNP, and their median home price was 60 percent higher than in counties carried by Trump.

These economically ascendant counties, largely urban, are geographically isolated. Hence the archipelago — islands of the relatively privileged surrounded by what is, to them, a mare incognitum, in which the less educated and more aggrieved dog paddle to survive.

One recalls the film critic Pauline Kael, who wondered aloud how George McGovern lost when everyone she knew had voted for him. However silly, Kael’s observation was a precursor of the “wasted vote phenomenon,” wherein Democrats roll up huge margins in blue enclaves, only to be thwarted by the tripartite menace of the electoral map, gerrymandering, and demographic sorting.