Every two years, on the first Tuesday of November, Americans head to the polls to vote in a federal election. This year, all eyes are on the US Congress. The Democrats are locked in an electoral struggle with the Republicans over both houses of the legislature, and the outcome will help determine the course of President Obama’s final two years in office. The Senate in particular is hotly contested, where majority control will be determined by the results of a handful of seats.

It hasn’t always been this way. The Constitution as originally written had no provisions for the direct election of US Senators. Why was this so, and how did it change?

The states of the United States met during the Constitutional Convention of 1787 to replace the Articles of Confederation. Edmund Rudolph of Virginia proposed a bicameral legislature, both based on the size and proportion of a state’s population. The lower house would be directly elected, while the members of the upper house would be nominated by their state legislatures and ratified by the lower house. Smaller states feared their influence in the national government would suffer. So William Patterson of New Jersey proposed a single chamber where each state would have equal representation. The two plans were known as the Virginia Plan and New Jersey plan. Neither had enough support to pass.

A committee made up of one delegate from each state met to resolve the issue. Their report recommended two houses, an upper house where each state had an equal vote, and a lower house where each state would have one delegate per 40,000 inhabitants, with slaves only counting as three-fifths of a person for the purposes of representation. This compromise, known as the Connecticut Plan, was eventually adopted, and Article 1 of the Constitution created the Senate and House of Representatives.

Originally, Senators were chosen by their state legislatures for a term of six years. The Founders believed that connecting the Senate and the state legislatures would inspire confidence and create strong national bonds. Critics claimed that this system was open to corruption and deadlock as men bought their Senate seats or factions in the legislatures could not agree on a Senate candidate. As early as 1826, people began to call for a Constitutional amendment providing for the direct election of Senators. While only a handful of elections were contested for impropriety, deadlock became a serious problem. In the 1850s, the Indiana State legislature was so contentious that one Senate seat sat vacant for two years. Between 1899 and 1903, legislative deadlock meant that Delaware only had one Senator.

The movement to bypass state legislatures picked up steam in the latter half of the nineteenth century, as voters became increasingly nervous that big businessmen were buying Senators. The Populist Party wrote a direct election plank into their platform in 1892, and in 1908, Oregon passed a law authorizing the direct election of Senators by popular vote. William Randolph Hearst used his publishing empire to promote the cause. In 1906, he published a series of articles by David Graham Phillips in his magazine Cosmopolitan. The series, entitled “The Treason of the Senate”, exposed senators as pawns of industrialists and financial institutions. Nationwide, public support for an amendment grew.

State legislatures also petitioned Congress for direct election of Senators. Beginning in 1893, the House had the two-thirds majority necessary to pass an amendment. Support in the Senate was predictably poor, and the bill failed. Subsequent attempts in 1900, 1904, and 1908 fared no better. By 1910, thirty-one states had passed resolutions supporting direct election. Additionally, fourteen of the incoming Senators that year had been elected through party primaries, and more than half the states had some form of election for Senate nominees. The writing was on the wall.

The House passed Joint Resolution 39 in 1911, proposing a constitutional amendment for the direct election of Senators. The bill went to the Senate, where it was changed to remove a provision preventing federal intervention in cases of racial discrimination in elections. The bill sat for the rest of the year. Growing impatient, the legislatures of twenty-seven states called for a constitutional convention to push for the amendment.

In the spring of 1912, the House finally voted for the Senate’s version of the bill, and on May 13, 1912, the amendment went to the states. Massachusetts wasted little time, voting in favor of the amendment on May 22. On April 8, 1913, Connecticut became the 36th state to ratify, and the Seventeenth Amendment became part of the United States Constitution on May 31, 1913.

The ratification process was not unanimous. Delaware and Utah both rejected the amendment, while eleven states took no action prior to ratification. Louisiana eventually ratified the Seventeenth Amendment in June 11, 1914. The last state to ratify the amendment was Rhode Island, on June 20, 2014, just over one hundred years later. Six states have still not ratified the amendment; Florida, Virginia, Georgia, Kentucky, Mississippi and South Carolina.

Controversy over the 17th Amendment continues today. Tea Party leaders are spearheading a new movement to repeal the amendment, returning appointment of Senators to the states. Sen. Ted Cruz criticized the amendment last year, saying he believed the amendment actually eroded states rights and led to the modern expansion of federal power. But the roots of the direct election of Senators came not from the federal government, but from citizens trying to make sure their representatives were neither the tools of business nor the pawns of state politicians.