The Case of the Vanishing Moderates
3
“The Case of the Vanishing Moderates:
Party Polarization in the Modern Congress”
The two political parties in Congress are as ideologically distinct as they
have been at any point in the last three decades. Scholars, analyzing the factors that
have propelled this polarization, have come to different conclusions. Several recent
studies find that fundamental shifts in party strategies inside Congress have polarized
the parties (Collie and Mason 2000 and Roberts and Smith 2003), while others claim
that the shift in the electorate has driven party divergence (Fleisher and Bond 2003
and Stonecash et al. 2003). This article takes two necessary steps back to analyze
party polarization. First, I explore the underlying mechanisms that have given rise to
the trend. Roughly one-third of the party polarization results from individual
member adaptation while two-thirds come from the replacement of moderate
members by more ideologically extreme members. Second, I discuss the extent of
the polarization that has occurred. In short, the Congress is between 70 and 100
percent more polarized in the 106
th
Congress than it was in the 92
nd
Congress.
After surveying the positions of the major political parties in 1968, George Wallace, a third-
party presidential candidate, famously remarked, “There ain’t a dime’s worth of difference” between
them. In some ways, his quote reflected cutting edge work in political science. Anthony Downs
(1957) predicted that as these electoral coalitions raced toward the political middle in hopes of
capturing the pivotal “median voter,” political parties would, under certain conditions, converge. The
ideological positioning of the congressional parties at the end of the twentieth century could not have
looked more different than the parties Wallace observed. In fact, Bill Clinton assumed the divergence
of the congressional parties when he developed his “triangulation” strategy. By rising above the
infighting of congressional Democrats and Republicans in Congress, Clinton hoped that he would
appear to be “above politics” in promising to stake out a “third way.”
In the race to the ideological poles, the parties left a vast middle sparsely populated. In 1968,
when Wallace made his acute observation, 61 percent of members were in the middle.
1
In 1998, the
percentage of members in the middle third of the ideological continuum was halved to 28 percent.
1
Throughout this article, I analyze Poole-Rosenthal (1997) DW-NOMINATE scores. Roughly, they exist on a
–1 (liberal) to +1 (conservative) scale. If we divide the continuum into three equal parts, the scores in the
ideological middle are from –0.33 to +0.33.
Convention