WordNet sense 1 (a person who backs a politician or a team etc.):

admirer, booster, champion, protagonist, supporter

WordNet sense 2 (an associate who provides assistance):

ally, ally

WordNet sense 3 (a person with whom you are acquainted):

acquaintance

WordNet sense 4 (a member of the Religious Society of Friends founded by George Fox (the Friends have never called themselves Quakers)):

Quaker