I've seen plenty of Chinese, Vietnamese, and Indians on posters in the Bay Area. (US representative for my district is Mike Honda) I have not seen many Arabs or Sikhs, but that may be more a function of population percentage and profession, than racism towards these groups, which exploded mostly after 9/11.

People who run for office are usually lawyers, and there is a definite ethnic divide in professions. Moreover, immigrants usually don't come to be lawyers, since being good at law requires a mastery of the language and the nuances of the local culture, and native born citizens have a natural advantage.