Fairfield, Connecticut, doesn’t look like the Donald Trump country you’re used to seeing. The stately homes in Greenfield Hill, with its two-acre zoning requirement, and the charming waterfront in Southport, with sailboats docked in the calm waters of Long Island Sound don’t gibe with the raucous rallies thrown by the Republican frontrunner. But these wealthy Connecticut suburbs are as much hotbeds of Trump support as some coal-mining counties in Kentucky. Statewide, Trump won the April 26 primary with 58% of the vote, including all but three cities in Fairfield County, home to some of the richest communities in America and...