Replication data for: The Most Liberal Senator: Analyzing and Interpreting Congressional Roll Calls

The non-partisan National Journal recently declared Senator John Kerry to be the \"top liberal\" in the Senate based on analysis of 62 roll calls in 2003. Although widely reported in the media (and the subject of a debate among the Democratic presidential candidates), we argue that this characterization of Kerry is misleading in at least two respects. First, when we account for the \"margin of error\" in the voting scores -- which is considerable for Kerry given that he missed 60%of the National Journal’s key votes while campaigning -- we discover that the probability that Kerry is the \"top liberal\" is only.30, and that we cannot reject the conclusion that Kerry is only the 20th most liberal senator. Second, we compare the position of the President Bush on these key votes; including the President’s announced positions on these votes reveals the President to be just as conservative as Kerry is liberal (i.e., both candidates are extreme relative to the 108th Senate). A similar conclusion holds when we replicate the analysis using all votes cast in the 107th Senate. A more comprehensive analysis than that undertaken by National Journal (including an accounting of the margins of error in voting scores) shows although Kerry belongs to the most liberal quintile of the contemporary Senate, Bush belongs to the most conservative quintile.