American politicians have always liked to talk about how they were born in a log cabin (or the contemporary equivalent) and worked their way up. In anticipation of hearing a lot of tales of upward mobility, I did a systematic search for information on the class background of the 16 Republican candidates. I'll consider the father's job for all except Ben Carson, who was raised by his mother. In cases of fathers who changed careers, I took the job when the candidate was about 10, which means that Jeb Bush's father is counted as a businessman and Rand Paul's as a doctor.
I distinguished three classes: working class (employed doing manual work), middle class (manager, professional, or own a business or farm), and upper class (large employer). By this definition, only four of the candidates can claim the coveted working-class background. They are Ben Carson (mother had various unskilled jobs, including domestic servant), John Kasich (father was a mail carrier), Mike Huckabee (father was a firefighter), and Marco Rubio (father was a bartender). Ten had middle-class backgrounds, and two (Bush and Trump) had upper class backgrounds. At the time the candidates were growing up, in the country as a whole I think the breakdown would have been about 60% working class, 40% middle class, and only a few (less than 1%) upper class, so the middle and upper classes are over-represented among the candidates, which isn't surprising. I was struck by the fact that at least seven of the fathers were self-employed (I don't know about Chris Christie's). That makes sense given the ideology of the Republican party, but it may apply to both parties: since a politician in the United States is a kind of entrepreneur, children of self-employed people may have an affinity for the profession.
While I was at it, I also recorded the universities that the candidates had attended. Five had undergraduate degrees from Ivy League colleges, and one from Stanford. Except for Huckabee, all of the others had attended at least moderately selective colleges, as defined here.
PS: a spreadsheet with the occupations is here.