and Mark Begich (D-Alaska) were attacked for voting their party line. Former centrist senator Olympia Snowe (R-ME) remarked that the inability of moderate senators to get amendments onto the agenda was, “shocking.” In this article, I examine the effects of filling the amendment tree on each party. By filling the amendment tree, Reid effectively cut both parties, including his colleagues and the electorally vulnerable moderates of his party, out of the legislative early game of amending legislation. However, by looking at the amendments submitted for consideration, I find that moderate Democrats were no more or less likely than their colleagues to protest the procedure. Indeed, it was Republican moderates who were much less likely to submit an amendment when the procedure was used while their more conservative counterparts filed amendments in an act of protest. The use of the procedure did however, likely contribute to homogenizing the voting record of senators who relied on “maverick” or centrist voting records to win reelection. Indeed, the difference in voting records for moderate Democrats and their more ideological colleagues was statistically insignificant. The paper proceeds as follows. I begin with a description of what the filling the amendment tree procedure is and how the procedure works. Then I examine the theoretical reasons for what we should expect in terms of legislative participation. I follow this with an empirical look at the amendment process and voting records. I conclude with implications for the study and suggestions for future research. Senate Procedures
Moderates were less likely than both liberals and conservatives to propose an amendment on a bill in which the amendment tree was filled. We also see some evidence of positive control from the Democratic leadership as there are fewer amendments submitted to the congressional record from liberals than there are conservatives. This supports the notion that senators use the ability to submit amendments as a method to register their displeasure with both the legislation and the process. Interestingly however, moderates are not using the procedure to register their displeasure with the legislation or the process, suggested that they are either okay with the substance of the legislation, or that they are fully entrusting the party leadership. Still, this is a descriptive cut of the data, and requires a more rigorous look. Table 1 summarizes the results of a negative binomial regression predicting the number of amendments submitted by Republicans when the amendment tree was filled. [Insert Table 1 here] The results of the negative binomial regression largely confirm the descriptive results. The distance from the middle variable is significant at the .1 level and positive, suggesting that the further a senator sits from the ideological center of the chamber, the greater the number of amendments they submit. Figure 2 illustrates the change in predicted number of amendments by the ideological distance from the center. The difference between the most moderate Republican and the most conservative Republican is approximately one amendment. [Insert Figure 2 here] Despite the logic of using the amendment process to signal constituents, the variables measuring senators in the election cycle were not significant. Similarly, retiring senators and bill sponsors, did not propose significantly more or less amendments. Vulnerability also had no
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