campaigner

noun4

1. •
   A person who campaigns for a person running for political office or works, or supports, in an organised and active way towards a goal; an activist.

   • It is remembered unfondly by politicians, communities and campaigners as the document that heralded widespread reductions in the size of the railway. — 2023
2. •
   Someone with experience in a certain field.
3. •
   A person who has served in a military campaign.
4. •
   A military veteran.