The Seventeenth Amendment (Amendment XVII) to the United States Constitution was passed by the Senate on June 12, 1911, the House of Representatives on May 13, 1912, and ratified by the states on April 8, 1913. The amendment supersedes Article I, § 3, Clauses 1 and 2 of the Constitution, transferring Senator selection from each state's legislature to popular election by the people of each state. It also provides a contingency provision enabling a state's governor, if so authorized by his state's legislature, to appoint a Senator in the event of a Senate vacancy until either a special or regular election to elect a new Senator is held.
Originally, each Senator was to be elected by his state legislature to represent his state, providing one of the many American governmental checks and balances. The delegates to the Convention also expected a Senator elected by his state's legislature would be able to concentrate on the governmental business at hand without direct, immediate pressure from the populace of his state, also aided by a longer term (six years) than the one afforded to members of the House of Representatives (two years). This process worked without major problems through the mid-1850s, when the American Civil War was in the offing.
Because of increasing partisanship and strife, many state legislatures failed to elect Senators for prolonged periods. For example, in Indiana the conflict between Democrats in the southern half of the state and the emerging Republican Party in the northern half prevented a Senate election for two years. The aforementioned partisanship led to contentious battles in the legislatures, as the struggle to elect Senators reflected the increasing regional tensions in the lead up to the Civil War.