In 2016, my vantage point on the donnybrook between Donald and Hillary was an Irish bar in Queens, where I was a bartender a few nights a week. It was a cash-only joint that sometimes stayed open until 7 a.m. and sold discounted cigarettes driven up from Virginia, the sort of place where you could make $800 under the table but you also might get a bottle or a chair thrown at you. This was where I watched the presidential debates and noticed something interesting. Half the patrons were Irish immigrants who considered Mr. Trump a real “eejit,” but the other half, the Irish Americans, thought he was just grand.

Something didn’t compute. Weren’t the Clintons universally beloved by all with Irish blood? (See “Derry Girls” on Netflix for a sample of the rock star treatment they got after Bill brought peace to Northern Ireland.) It was puzzling to watch the barflies buzz about Trump’s anti-immigration rhetoric — a drawbridge mentality from a crowd whose lineage had been met with “Irish Need Not Apply” signs. The craic in the Queens shebeen turned out to be a sudsy microcosm: The green vote has never been more red.

“All those Irish were Democrats for literally hundreds of years,” said James F. McKay III, the president of the Ancient Order of Hibernians, the largest Irish Catholic organization in the country. “But what is the old saying? When they got the wrinkles out of the belly, they became Republicans.”

No doubt. My own grandfather, one of 12 children raised in a two-bedroom house in County Armagh, sailed to Philadelphia, and cheered when John F. Kennedy became president. Sixty-six years later, some of my grandfather’s children and his brother voted for Donald Trump.