Back in the early 20th century, Eugene Debs, a former railway worker and labor organizer, turned to radical politics after leading strikers in a confrontation with federal troops and spending six months in jail for contempt of court. Debs joined the Socialist Party, and ran as the party's presidential candidate in 1900, 1904, 1908 and 1912. He lost all those elections, but in 1916, he chose to run for a Congressional seat in Indiana, on a pacifist platform, and actually won.
Even then, Debs managed to get in trouble. After the U.S. joined the Allied side in World War I, Congress passed the Espionage and Sedition acts which essentially made it a crime to publicly oppose the war. After Debs ignored the law and gave an "anti-war speech" (just one line mentioned the war) in Canton, Ohio, he was arrested, tried and convicted, and sentenced to 10 years in a federal penitentiary in Atlanta.
But that didn't stop Debs from running for president a fifth time from behind bars. His supporters portrayed him as a martyr for civil liberties, and even likened him to Abraham Lincoln and Jesus Christ. He managed to get 919,000 votes, about 3.5 percent of the total cast. The following year, newly elected President Warren G. Harding freed him from prison [sources: PBS, Britannica, Kansasheritage.org].