a person who puts forward a proposition or proposal.

a person who argues in favor of something; an advocate.

a personwho supports a cause or doctrine; adherent.

a person who propounds a legal instrument, such as a will for probate.

noun

enemy , foe , opponent

noun

advocate , backer , champion , defender , enthusiast , exponent , expounder , friend , partisan , patron , protector , second , seconder , spokesperson , subscriber , supporter , upholder , vindicator , booster