Only three of the 25 largest cities in America now have Republican mayors. In the House of Representatives, Republicans from dense urban congressional districts have become extinct. In the 2012 presidential election, the counties containing Manhattan, the Bronx, Brooklyn, Washington, San Francisco and Philadelphia each gave less than 20 percent of their vote to Mitt Romney. In this coming election, Donald J. Trump is unlikely to do better — and may fare worse.
In the 1950s, in presidential election results compiled by the Stanford political scientist Jonathan Rodden, a county’s population density was a poor predictor of how its residents voted. Today, the pattern is remarkably consistent: The denser the county, the more overwhelmingly its residents vote Democratic.
The anti-city strategy holds up today only because Democrats, with their tight clusters of urban support, are at a structural disadvantage in Congress.
“One of the most important implications of all this is that ignoring cities can be a winning strategy in House races,” Mr. Rodden said. “The mix of positions that the Republicans have taken has served them really well in winning the House. But it’s not working out so well in presidential elections.”