Ron Brownstein at the Atlantic has written extensively about how those without a college degree back Trump and those with a college degree oppose him. The “poorly educated” as the GOP frontrunner affectionately (maybe) calls them. This split has been consistent in the exit polls. This divide also comes through looking at individual counties. Virginia has 133 cities and counties. A strong correlation exists (-.81) between Trump vote share and the percentage of people (25 year old and older) in the city/county with at least an Associates Degree.
A positive correlation (+.855) occurs between the share of Kasich and Rubio support and attaining a degree.
Trump picked the right demographic group to build a durable base on. Ted Cruz staked his on religiosity and ideology. That’s good to win Iowa and a few other states, but when the race moves to the northeast, west coast, or Rust Belt, the deeply religious and conservative simply don’t exist in the same numbers. People without a college degree though, make up significant shares of the electorate everywhere. It’s how Trump can win in Alabama and Massachusetts, especially with multiple candidates dividing up support of college graduates.