Political affiliation is a protected class in California[0] but this may be legal in some states.

[0] https://www.nolo.com/legal-encyclopedia/california-employmen...

That's only for employers discriminating against employees. It doesn't apply to customers -- a business can almost always refuse to do business with you, for almost any reason. Example: you can get thrown out of a restaurant for not adhering to a dress code.

Good catch! I'm not sure what I was thinking.

I did some further searches; Madison, Wisconsin[0] and DC[1] forbid discrimination on political affiliation in public accommodations.

[0] https://library.municode.com/wi/madison/codes/code_of_ordina...

[1] https://ohr.dc.gov/protectedtraits

Sure thing. Right next to the commonplace "no shirt, no shoes, no service" and "we reserve the right to refuse service to anyone" signs.