I think the ethnic associations with the drinks to select from don't coincide with the ethnicity of the person associated with them
McCain would be better suited for Hawaiian Punch, white as he is.
Bill Clinton would best be associated with Kool-aid, him being considered the first black president by some.
Obama deserves to be Purple Drank, since he is effectively the blackest Candidate to choose from, and you white boys know nothing about purple stuff.
Hillary deserves to be compared to Cyanide.