/ kæmˈpeɪnə(r); NAmE / noun
a person who leads or takes part in a campaign, especially one for political or social change :
a leading human rights campaigner
a campaigner on environmental issues
a campaigner for women priests
an old / veteran / seasoned campaigner (= a person with a lot of experience of a particular activity)
( especially NAmE )
Bush campaigners (= people working for Bush in a campaign)