A person who supports a person, idea, movement, or organization. Neutral term; can be used in political, social, or personal contexts.
He is an enthusiastic supporter of that politician.
This plan has many backers.
支持者 is a formal term for a supporter, often in political contexts, while 味方 is a broader, everyday word for an ally.
支持者 stresses active support for a person's views or cause, whereas フォロワー just means someone who follows, without implying agreement.
支持者 refers to someone who actively supports a cause, policy, or person (like a politician), while ファン is broader and can apply to entertainment or sports without implying active backing.
Compound of 支持 (support) + 者 (person). The word is a straightforward Sino-Japanese formation.