Campaigner (noun)

A person who takes part in a political campaign or works to achieve a specific goal.

Origin:

From campaign + -er.

Examples:

1. She was a passionate campaigner for women's rights and worked tirelessly to promote equality.
2. The campaigner was successful in raising awareness about the issue and pushing for change.
3. The environmental campaigner was invited to speak at the United Nations about climate change.
4. The campaigner's efforts were supported by a large network of volunteers and donors.
5. The health campaigner was determined to find a cure for the rare disease and never gave up.