On May 12, 1912, the Seventeenth Amendment, providing for direct popular election of the Senate, was approved by Congress; the requisite three-fourths of the state legislatures ratified it in less than eleven months. Not only was it ratified quickly, but it was also ratified by overwhelming numbers. In fifty-two of the seventy-two state legislative chambers that voted to ratify the Seventeenth Amendment, the vote was unanimous, and in all thirty-six of the ratifying states the total number of votes cast in opposition to ratification was only 191, with 152 of these votes coming from the lower chambers of Vermont and Connecticut.

Although state ratification of the Seventeenth Amendment came quickly and easily, congressional approval of the idea of popular election of the Senate did not. The first resolution calling for direct election of the Senate was introduced in the House of Representatives on February 14, 1826. From that date, until the adoption of the Seventeenth Amendment eighty-six years later, 187 subsequent resolutions of a similar nature were also introduced before Congress, 167 of them after 1880. The House approved six of these proposals before the Senate gave its consent. By 1912, senators were already picked by direct election in twenty-nine of the forty-eight states. As Senator William E. Borah said in 1911, “I should not have been here [in the U.S. Senate] if it [direct election] has not been practiced, and I have great affection [for this system].” Most states had gradually turned to non-binding primary elections to select their senators; state legislators promised to vote for the candidate that the people had selected in this “advisory” election. This “advisory” election had real teeth because many state laws provided that candidates for state legislator had to sign pledges (which were placed on the ballot) that they would promise (or refuse to promise) to vote for the U.S. Senate candidate that the people had selected in their nonbinding election.

If the state legislative candidate refused to sign the pledge, the people would vote against him, and so the Senate gradually became populated with people who were, in effect, selected by popular, direct election.

The Seventeenth Amendment was approved and ratified to make the Constitution more democratic. Progressives argued forcefully, persistently, and ultimately successfully that the democratic principle required the Senate to be elected directly by the people rather than indirectly through their state legislatures. By altering the manner of election, however, they also altered the principal mechanism employed by the Framers to protect federalism. The Framers understood that the mode of electing (and especially reelecting) senators by state legislatures made it in the self-interest of senators to preserve the original federal design and to protect the interests of states as states (see Article I, Section 3, Clause 1). This understanding was perfectly encapsulated in a July 1789 letter to John Adams, in which Roger Sherman emphasized that “[t]he senators, being eligible by the legislatures of the several states, and dependent on them for re-election, will be vigilant in supporting their rights against infringement by the legislative or executive of the United States.”

In practice, the state legislatures’ election of senators became more complicated. The members of the state legislators were often divided over whom to elect as senator. Many state legislators simply voted for themselves, and their deadlock would result in no senator’s being chosen, which then deprived the state of any representation in the Senate for a year or more.

In addition to its effect on federalism, the ratification of the Seventeenth Amendment has also had demographic, behavioral, and institutional consequences on the Senate itself. Demographically, popularly elected senators are more likely to be born in the states they represent, are more likely to have an Ivy League education, and are likely to have had a higher level of prior governmental service. Institutionally, the states are now more likely to have a split Senate delegation, and the Senate now more closely matches the partisan composition of the House. Additionally, the amendment makes problematic the assertion in Garcia v. San Antonio Metropolitan Transit Authority (1985) that the political process in the Senate is sufficient to protect the states’ sovereign interests against expansive federal legislation.