sympathizer (n.)

• abettor
• accessory
• accomplice
• acquaintance
• admirer
• advocate
• aficionado
• ally
• angel
• apologist
• approver
• backer
• brother
• buff
• champion
• collaborator
• confidant
• confidante
• conspirator
• defender
• dependence
• endorser
• exponent
• familiar
• fan
• fellow
• friend
• intimate
• lover
• mainstay
• maintainer
• neighbor
• partisan
• patron
• pickup
• promoter
• protagonist
• reliance
• repository
• second
• seconder
• sectary
• sider
• sponsor
• stalwart
• standby
• support
• supporter
• sustainer
• upholder
• votary
• well-wisher