-MA's less populous counties have lots of colleges, maybe?
Not particularly. They're just fairly Anglo, Vermont-like rural areas (Hampshire, Franklin and Berkshire Counties) or resort islands (Dukes/Martha's Vineyard, Nantucket).
Hampshire County does contain the Five Colleges, and Williams is in Berkshire County, but Williams contributes only a negligible amount of the Berkshire County vote, and of the Five Colleges, only UMass-Amherst is particularly large. Most MA college students are in Suffolk (BU, BC, Northeastern, UMass-Boston, etc.) or Middlesex (Harvard, MIT, Tufts, Brandeis, etc.) Counties.