become a partisan

See: espouse
References in classic literature ?
You are bound either to fall a victim or to become a partisan in this incessant strife of ambitions, desires, and hatreds, in the midst of which you are placed; and by slow degrees the picture of vice triumphant and virtue made ridiculous produces its effect on a young man, and he wavers; life in Paris soon rubs the bloom from conscience, the infernal work of demoralization has begun, and is soon accomplished.
So," D'Artagnan resumed, "you will not become a partisan of Mazarin's?