Supporter, n.
1. One who, or that which, supports; as, oxygen is a supporter of life. The sockets and supporters of flowers are figured. Bacon. The saints have a . . . supporter in all their miseries. South.
2. Especially, an adherent; one who sustains, advocates, and defends; as, the supporter of a party, faction, or candidate.
3. (Shipbuilding)
A knee placed under the cathead.
4 more senses
4. (Her.)
A figure, sometimes of a man, but commonly of some animal, placed on either side of an escutcheon, and exterior to it. Usually, both supporters of an escutcheon are similar figures.
5. (Med.)
A broad band or truss for supporting the abdomen or some other part or organ.
Shades of meaning
Fernald has no entry of its own for supporter; he lists it under adherent.
Where he writes about it:
One may be an aider and supporter of a party or church, while not an adherent to all its doctrines or claims. — from adherent
One may be an adherent or supporter of a party and not a partisan. — from adherent