Is political affiliation a protected class?

[Bart H.]

OK BP's community,  out of curiosity, could a landlord or someone say looking for a roommate advertise that they didn't want to rent to a supporter of a certain political party?  or politician (say Trump)? 

MY question is not about debating the merits of any one politician or party, but rather could you legally discriminate on political beliefs?  Could political beliefs fall under the religion classification?

Thoughts?