During the Civil War, Tilden guardedly supported the Union war effort and dissociated himself from the Peace wing of the Democratic party; yet he vociferously criticized Republican policies, such as emancipation, paper currency, and the draft. He opposed radical plans for Reconstruction, supporting, instead, President Andrew Johnson’s Reconstruction program.

Tilden served as chairman of the New York State Democratic Committee, 1866-1874, and was Horatio Seymour’s national campaign manager during the 1868 presidential election. Tilden gained significant public exposure for his role in destroying the notorious Tweed Ring in New York City. Although initially reluctant to attack fellow Democrats, he teamed with the prestigious Committee of Seventy to help topple that corrupt political machine. He used his new credentials as a reformer to gain election to the state legislature in 1872 and the governorship in 1874. As governor, he added to his reform reputation by bringing the corrupt Canal Ring to justice.

In 1876, given his national renown as a reformer and his position as governor of an electoral giant of a state, the Democrats overwhelmingly nominated Tilden for president on the second ballot. The Democratic platform condemned the corruption of the Grant administration, called for an end to the Reconstruction experiment, tariff reform, a ban on Chinese immigration, and a halt to federal railroad subsidies. While Tilden won a majority (51%) of the popular vote, the electoral votes in South Carolina, Louisiana, and Florida (and one in Oregon) were disputed, causing a special commission to decide the election. All disputed ballots were granted to the Republican candidate, Rutherford B. Hayes, who was consequently elected president by one electoral vote. Although displeased, Tilden reacted with equanimity throughout the controversy and accepted the final outcome.