Campaigner

A Campaigner is someone who is participating in a campaign by:

Voting on campaign matters and (or has authorised some other entity to use their vote)
Has made an unofficial promise to act personally in accordance with the campaign goals

A campaigner can resign from any campaign anytime thus lowering the weight of the campaign.
A campaigner cannot be a member of multiple campaigns directed at the same entity at a single time, so one has to choose the campaign that seems to have the best argumentation, research, view of the world or popularity.