companion; person accompanying someone
Neutral term for a person who goes along with another, often in a social or travel context.
May I bring a companion to the party?
He attended the meeting as an accompanying person.
Refers to someone who supports a group, movement, or ideology without being a formal member; often used in political or ideological contexts. Cross-referenced with 同調者.
See also: 同調者
He is not a party member, but a long-time fellow traveler.
The movement had many sympathizers.
同伴者 is a formal, often official word for an escort or companion, whereas 連れ is the casual, everyday term for someone you're with.
Compound of 同伴 (dōhan, 'accompanying') + 者 (sha, 'person'). The political sense is a calque from English 'fellow traveler'.