https://en.m.wikipedia.org/wiki/Eugene_V._Debs

Early in his political career, Debs was a member of the Democratic Party. He was elected as a Democrat to the Indiana General Assembly in 1884. After working with several smaller unions, including the Brotherhood of Locomotive Firemen, Debs led his union in a major ten-month strike against the CB&Q Railroad in 1888. Debs was instrumental in the founding of the American Railway Union (ARU), one of the nation's first industrial unions. After workers at the Pullman Palace Car Company organized a wildcat strike over pay cuts in the summer of 1894, Debs signed many into the ARU. He led a boycott by the ARU against handling trains with Pullman cars in what became the nationwide Pullman Strike, affecting most lines west of Detroit and more than 250,000 workers in 27 states. Purportedly to keep the mail running, President Grover Cleveland used the United States Army to break the strike. As a leader of the ARU, Debs was convicted of federal charges for defying a court injunction against the strike and served six months in prison.

In prison, Debs read various works of socialist theory and emerged six months later as a committed adherent of the international socialist movement. Debs was a founding member of the Social Democracy of America (1897), the Social Democratic Party of America (1898) and the Socialist Party of America (1901). Debs ran as a Socialist candidate for President of the United States five times: 1900 (earning 0.6 percent of the popular vote), 1904 (3.0 percent), 1908 (2.8 percent), 1912 (6.0 percent), and 1920 (3.4 percent), the last time from a prison cell. He was also a candidate for United States Congress from his native state Indiana in 1916.

Debs was noted for his oratorical skills, and his speech denouncing American participation in World War I led to his second arrest in 1918. He was convicted under the Sedition Act of 1918 and sentenced to a 10-year term. President Warren G. Harding commuted his sentence in December 1921. Debs died in 1926