Joe Miller, Alaska’s Republican nominee for the United States Senate, recently expressed support for an idea that is rapidly gaining steam in Tea Party circles: the repeal of the Seventeenth Amendment. Miller subsequently backtracked from his statement, but he shouldn’t have: Repealing the Seventeenth Amendment would go a long way toward restoring federalism and frustrating special-interest influence over Washington.

Ratified in 1913, the Seventeenth Amendment replaced the election of U.S. senators by state legislators with the current system of direct election by the people. By securing the Seventeenth Amendment’s ratification, progressives dealt a blow to the Framers’ vision of the Constitution from which we have yet to recover.

The Constitution did not create a direct democracy; it established a constitutional republic. Its goal was to preserve liberty, not to maximize popular sovereignty. To this end, the Framers provided that the power of various political actors would derive from different sources. While House members were to be elected directly by the people, the president would be elected by the Electoral College. The people would have no direct influence on the selection of judges, who would be nominated by the president and confirmed by the Senate to serve for life or “during good behavior.” And senators would be elected by state legislatures.

Empowering state legislatures to elect senators was considered both good politics and good constitutional design. At the Constitutional Convention in Philadelphia, the proposal was ratified with minimal discussion and recognized as the approach “most congenial” to public opinion. Direct election was proposed by Pennsylvania’s James Wilson but defeated ten to one in a straw poll. More important than public opinion, however, was that limitations on direct popular sovereignty are an important aspect of a constitutional republic’s superiority to a direct democracy. As Madison observes in Federalist 51, “A dependence on the people is, no doubt, the primary control on the government; but experience has taught mankind the necessity of auxiliary precautions.”

Election of senators by state legislatures was a cornerstone of two of the most important “auxiliary precautions”: federalism and the separation of powers. Absent some direct grant of federal influence to state governments, the latter would be in peril of being “swallowed up,” to use George Mason’s phrase. Even arch-centralizer Hamilton recognized that this institutional protection was necessary to safeguard state autonomy. In addition, the Senate was seen as a means of linking the state governments together with the federal one. Senators’ constituents would be state legislators rather than the people, and through their senators the states could influence federal legislation or even propose constitutional amendments under Article V of the Constitution.

The Seventeenth Amendment ended all that, bringing about the master-servant relationship between the federal and state governments that the original constitutional design sought to prevent. Before the Seventeenth Amendment, the now-widespread Washington practice of commandeering the states for federal ends — through such actions as “unfunded mandates,” laws requiring states to implement voter-registration policies that enable fraud (such as the “Motor Voter” law signed by Bill Clinton), and the provisions of Obamacare that override state policy decisions — would have been unthinkable. Instead, senators today act all but identically to House members, treating federalism as a matter of political expediency rather than constitutional principle.

There is no indication that the supporters of the Seventeenth Amendment understood that they were destroying federalism. But they failed to recognize a fundamental principle of constitutional design: that in order for constraints to bind, it is necessary for politicians to have personal incentives to respect them. “Ambition,” Madison insisted in Federalist 51, “must be made to counteract ambition. The interest of the man must be connected with the constitutional rights of the place.”

Under the original arrangement, senators had strong incentives to protect federalism. They recognized that their reelection depended on pleasing state legislators who preferred that power be kept close to home. Whereas House members were considered representatives of the people, senators were considered ambassadors of their state governments to the federal government and, like national ambassadors to foreign countries, were subject to instruction by the parties they represented (although not to recall if they refused to follow instructions). And they tended to act accordingly, ceding to the national government only the power necessary to perform its enumerated functions, such as fighting wars and building interstate infrastructure. Moreover, when the federal government expanded to address a crisis (such as war), it quickly retreated to its intended modest level after the crisis had passed. Today, as historian Robert Higgs has observed, federal expansion creates a “ratchet effect.”