Which of the following demonstrates early civil service reform in the late nineteenth century?

Debs is accurately described as the leader of the American Railway Union and was jailed for his role in the Pullman strike, which directly aligns with the question's criteria. He later became a significant figure in the Socialist Party of America, advocating for workers' rights throughout his career.

Gompers was the founder of the American Federation of Labor (AFL), focusing on skilled labor and collective bargaining rather than the broader socialist movements of Debs. He did not lead the American Railway Union and was not jailed in connection with the Pullman strike.

Haywood was a leader of the Industrial Workers of the World (IWW) and was known for radical labor activism; however, he did not lead the American Railway Union and was not specifically associated with the Pullman strike or the Socialist Party in the same way Debs was.

Thomas was a later leader of the Socialist Party of America, but he did not participate in the Pullman strike or lead the American Railway Union. His political career began after Debs had already established himself in socialist politics.