Three Senate races from last Tuesday’s election remain undecided today, with one race (Minnesota’s) down to only a 204-vote margin. In light of the impact each and every vote has in these races, it bears remembering that the principle of “one person, one vote” has only applied in the election of U.S. Senators since the progressive constitutional reforms of the early 20th century.

Under the original Constitution, U.S. Senators were chosen not by the people, but by state legislators. Article 1, Section 3 of the Constitution provides that “the Senate of the United States shall be composed of two Senators from each state, chosen by the legislature thereof, for six years; and each Senator shall have one vote.” The 17th Amendment, ratified in 1913, was part of a wave of progressive constitutional reforms that sought to make the Constitution, and our nation, more democratic. It gave Americans the right to vote directly for their Senators, thereby strengthening the link between citizens and the federal government. In addition to the 17th Amendment, the first half of the 20th century saw the ratification of two other important progressive amendments: the 16th Amendment, also ratified in 1913, which allowed for a truly progressive federal income tax, and the 19th Amendment, ratified in 1920, which extended the vote to women.

As Yale Law Professor Akhil Reed Amar writes in America’s Constitution: A Biography, the 17th Amendment had the effect of improving legislative accountability at both the state and federal levels. State legislators, for example, were now spared the time-consuming, and often corrupting, process of being quietly lobbied by individuals interested in becoming senators. And directly-elected senators found it easier to support policies that served citizens but that may not have been so popular among state legislators, thereby making the federal government more directly responsive to the electorate.

This week, all Americans should be celebrating this shift toward direct popular election of the Senate. As the recounts and runoffs in Georgia, Alaska, and Minnesota get under way, the importance of each and every vote in Senate races will be on full display, just as is our Constitution’s history as an increasingly inclusionary, and fundamentally progressive, document.