>(Working-class voters are defined here conventionally as voters lacking a college degree.)

Classism.

The ‘working class’ includes the vast majority of college grads.

I have a genetics degree, I work in healthcare and make a paycheck. I am working class. I was working class when I was a cook making a fraction as much.

I have no plans to start a business or become a landlord or do anything else that removes me from the working class.

Doctors who pull 400k in wages are working class.

Contractors, day laborers, service industry, firemen, chefs, fishermen, pathologists, dock workers, nurses, teachers, researchers, engineers. 

All who work to earn their wages are the working class.