Its black glass exterior soars high above Fifth Avenue, and its gold-tipped revolving doors have spun the likes of Bruce Willis and Anne Hathaway into its waterfall-splashed atrium. But on Election Day, Trump Tower earned a different sort of distinction: a tiny island of Romneyville amid Manhattan’s deep, blue-state sea. … Mr. Romney won a single Manhattan precinct outright, a stretch of Park Avenue near the Waldorf-Astoria, where six voters showed up and four chose the Republican. But he suffered a resounding defeat in New York, a rare outbreak of consensus in a city famous for fevered disagreement: in 91...