Someone who is a protagonist of an idea or movement is a supporter of it.
例句
...the main protagonists of their countries' integration into the world market.积极呼吁他们的国家融入世界市场的主要倡导者
N-COUNT
主人公;主角;(真实事件的)主要人物
A protagonist in a play, novel, or real event is one of the main people in it.
例句
...the protagonist of J. D. Salinger's novel 'The Catcher in the Rye'...塞林格的小说《麦田里的守望者》的主人公The chief protagonists in the row are Visa and Mastercard, the world's leading credit card brands.这场纠纷的主角是世界两大信用卡品牌——维萨和万事达。
英汉词典释义
n.
领导者;倡导者;拥护者
She was herself a vehement protagonist of sexual equality.她本人就热心提倡男女平等。
英英词典释义
Noun
1. a person who backs a politician or a team etc.;
"all their supporters came out for the game""they are friends of the library"