Seconder

(n.) One who seconds or supports what another attempts, affirms, moves, or proposes; as, the seconder of an enterprise or of a motion.

Thesaurus Entries

Maecenas, abettor, admirer, advocate, aficionado, angel, apologist, backer, buff, champion, defender, dependence, encourager, endorser, exponent, fan, favorer, friend at court, lover, mainstay, maintainer, paranymph, partisan, patron, promoter, protagonist, reliance, second, sectary, sider, sponsor, stalwart, standby, support, supporter, sustainer, sympathizer, upholder, votary, well-wisher