The Decline of Third-Party Voting in the United States

This paper documents and investigates a prominent but little discussed pattern in U.S. politics, which is the decline of third-party electoral support over the past century. We find evidence consistent with the claim that electoral support for third parties—mainly left-wing third parties—declined because the Democratic Party co-opted the left-wing policy position beginning with the passage of the New Deal agenda. We note first that most of the third-party voting in the pre-New-Deal era was for left-wing third parties and that this declined sharply during the 1930s and 1940s. We then show that after the New Deal the Democratic Party's electoral support was higher in areas that had traditionally supported left-wing third parties. Contrary to some claims in the literature, we find little support for the hypothesis that the decline of third-party voting was immediately due to electoral reforms such as the introduction of direct primaries and the Australian ballot, except possibly in the south.