A bit of googling reveals that Connecticut senatorial candidate Ned Lamont, the one-trick anti-Iraq pony, is the grand-nephew of Corliss Lamont, a monied Stalinist and later semi-ex-Stalinist who used to pay for full-page ads in the New York Times about one rosy cause or another.
Phillips Exeter and leftism seem to run in the family, which traces its money back to the House of Morgan.
History assignment for someone: Why did the Eastern upper bourgeoisie commit collective suicide over three or four generations?
Assignment two: How did Colonial Puritanism mutate into Transcendentalism and Unitarianism, and Southern New England become Irish, Italian and Catholic, leaving the Lowells, Cabots and Saltonstalls to comic verse ("The Lowells speak only to Cabots,/And the Cabots speak only to God?"), poetry and madness?
Steve Sailer might lay it all on immigration, but I think there's more to it than that.