A few notes upfront. The data on both social class and partisan affiliation are based on self-reports. Until the year 2000, the GSS question about racial identity included only three options–“white”, “black”, and “other”. Those who participated from 2000 onward and self-identified as Hispanic split evenly between “white” and “other” on the aforementioned ternary question. Roughly then, the whiter half of the country’s Hispanic population is included in these figures.
Working class whites:
They’ve steadily streamed out of the Democrat party over the last fifty years. The GOP has stubbornly managed to look a gift donkey in the mouth for decades, though, because they haven’t received a warm welcome from the Republican party. They haven’t really received a welcome at all. The party often appears embarrassed by their support. Donald Trump won the upper Midwest by finally inviting them into the lobby, but the party establishment is intent on keeping them locked outside the convention hall.
Middle class whites:
The pattern is similar but less pronounced and more GOP-friendly than among the working class. The rule of law, opposition to racial preferences, and a conscious effort to avoid being the marionettes of a 1% that generally despises it is a reasonable blueprint for the GOP to improve these numbers.
Upper class whites:
Democrats have hauled more in corporate donations than Republicans have since 2006. The last Republican presidential candidate to outraise his Democrat opponent was George W. Bush in 2004. Yet Republicans still catch the lion’s share of the flak for being the party of the rich. There’s a reason the GOP is often referred to as the Stupid Party.
Post-script, per commenter Saint Louis, lower class whites:
The trend is similar to to that of the working class with the entire curve shifted more towards Democrats.
GSS variables used: YEAR, PARTYID(0-1)(2-4)(5-6), RACE(1)