seceder

Example:He was considered a seceder from the political party because he favored a different agenda.

Definition:to leave or withdraw from a group, organization, or cause

Example:The movement to establish a secessionist government led to a significant political crisis.

Definition:a person who advocates or practices secession, specifically in the context of attempting to form an independent state by breaking away from an existing country

Example:During the American Civil War, several states seceded from the Union to form the Confederate States of America.

Definition:a state or region that has separated from a larger political entity and declared independence