Are amendment strategies learned through experience or contingent on the institution?

Seniority in Congress is a standard explanation for why some legislators are more effective lawmakers. Studies in political science reinforce this assumption with empirical observations that senior members are more likely to receive high profile committee positions (Bullock 1985; Roberts 1990; Price 2009) and pass more legislation (Schiller 1995; Berry and Fowler 2019). Similarly, in a LegBranch post in April, Andrew Taylor suggested each additional Congress served raises the probability a U.S. Representative enacts a sponsored bill into law by four percent. This logic reinforces the idea that one needs time to learn how Washington works before they can truly start winning the game.

Our study focuses on the U.S. Senate and observes all amendments submitted by senators from 1985 to 2015; a total of 66,527 amendments. We sought to determine whether individual senators alter their legislative behavior during their career. Therefore, we compare each senator to their own past legislative behavior to understand if seniority (or time in the Senate) changes the number of amendments each senator submits, how many are actually considered, and those that receive any roll call vote. The study also controls for individual characteristics that can change from congress to congress including; ideology, majority party status, and institutional influence which have been shown to be stronger predictors of which senators sponsor amendments (Carson, Madonna, and Owens 2013).

The findings of our study were presented at last month’s Midwest Political Science Association meeting in Chicago, IL. We found the power of the seniority hypothesis is not supported when you consider how legislators participate in the amending process. Seniority is simply the prerequisite to achieve the positions of power that enhance a senator’s ability to amend bills, but seniority on its own does not appreciably increase amendment submission or consideration.

Our estimates represent the probability of how many amendments a senator will submit, how many will be considered, and how many amendments will receive a roll call vote. We derive the estimates using count models (negative binomial) to examine the legislative activity senators during their careers. We look at each senator’s activity in each congress separately allowing us to make comparisons within and across senators. We control for a number of factors including; the prior amendment activity of each senator and the expanded use of filling the amendments tree since the 109^th Congress. In our model, we also account for a senator’s majority party status each congress; their ideology relative to the chamber; if the senator serves as a chamber or committee leader; is up for election; years of Senate service; the types of committees each senator serves (Deering and Smith 1997).

Stories of the Senate’s history describe victories by senators who became students of the institution. Therefore, we are primed to believe that senators generally offer more amendments and are more active as their careers progress. That fits with views of the Textbook Congress and the norm of apprenticeship to watch and observe before engaging in the lawmaking process. We found this is not the case. Senators, particularly political outsiders in the minority party jump right in (see Hall and Fowler’s on pork spending).

The estimates shown in Figure 1 predict the number of amendments senators offer in a given congress, based on specific individual characteristics. Estimates to the right of the red line indicate characteristics that increase the number of amendments a senator is likely to submit, have considered, or receive a roll call vote. Estimates to the left of that line signal when a senator’s amending activity should be less. From these results, we can ascertain senators that submit the most amendments are ideologically extreme members of the minority party, as well as senators that serve in a leadership capacity. The group of senators that sponsor fewer amendments than the average senator are ideologically extreme members of the majority party. We use the three levels of attention amendments receive that are discussed above to understand amendment strategies by senators during their career. Once we think of the 5,691 amendments receiving a roll call vote (procedural or passage), we find those sponsored by the Democratic and Republican Leaders of the Senate and ideologically extreme members of the minority party receive a roll call vote more often. This means the roll call record is generated not by most senators, but the activity of those members most institutionally strong and weakest institutionally.

Figure 1: Probability a Senator will Offer more Amendments than the Average Senator

The intuition that senators should offer more amendments in the congress they are up for election is not supported by these findings. Revisiting the seniority hypothesis, we do not find statistical support that senators sponsor more amendments as they serve additional terms in office. Moreover, all things equal, the Senate is not likely to consider more of a senator’s amendments as their career progresses either. The finding that seniority does not enhance the effectiveness of a senator raises a larger question. What characteristics of a legislator’s service significantly increase legislative activity creating the appearance that seniority matters?

Seniority is gained after voters recognize someone who can get things done. Those that wish to influence politics nationally seek promotion within the Senate to enhance opportunities to shape law via floor amendments and committee work (Fenno 1973; Kingdon 1989). Therefore, the expected influence of seniority reflects the overrepresentation of senior members leading a committee. From 1981-2015 the correlation between seniority and committee leadership was 0.51. The average seniority of committee leaders was an average of 22 years in the Senate compared to an average of 12 years of service for all others. Moreover, across the 30 year period of our study, two-thirds of the senators serving more than three terms were a committee chair or ranking member in each congress.

To better understand the interactive effect between partisan control and a legislator’s ideology on amendment activity, we estimate the marginal effect of a senator’s ideological distance (from the chamber mean) on their amendment activity. The magnitude of the effect is clearly seen by comparing the diverging lines in Figure 2. The red line represents the number of amendments from senators serving in the majority party, regardless of which party was in power. Conversely, the blue line represents amendments sponsored by senators from the minority party. The variation in these predictions captures senators’ different ideologies within the chamber.

Figure 2: Ideology’s Differing Effect on Amendment Activity by Party Status

The motivation of a legislator to sponsor amendments comes from their own individual characteristics relative to the political makeup of the Senate. Senators who have policy beliefs that are distinctly different from the rest of the Senate – and are thus more ideologically extreme —are more likely to offer amendments when they are in the minority party. Interestingly, the same ideologically distant members sponsor slightly fewer amendments when they are members of the majority party. The difference in how ideology interacts with serving as a member of the majority party suggests that past Majority Leaders have been successful at dissuading division within the party. The conditions where senators adapt their amendment strategies and what will receive a roll call vote in each Congress are confirmed by the predicted probabilities estimated by our model and data. If we think of this on a grand scale, there appear to be two motivations to add to the roll call record. One consists of ideologically distant senators that want to be seen fighting for policy, even if they lose. Another drives institutionally powerful senators that want to be seen winning and enhancing the party brand. While all senators have the ability to submit amendments, the primary difference is that our results suggest the perceived benefits of submitting an amendment are not distributed across the chamber equally.

Setting expectations about legislative behavior based on bill sponsorship has skewed our understanding of how institutionally advantaged and institutionally disadvantaged senators use other tools to influence legislation. Our study suggests that senators’ amendment activities – both their submission volume and how far they push those amendments – do not respond to seniority directly. Rather, their activity is shaped by institutional circumstances for themselves and their party. Overall, we find that senators are likely to offer more amendments when they are institutionally advantaged (leadership) and when they are likely to have partisan and ideological objections to legislation on the floor. Therefore, no matter how long a senator serves they are unlikely to introduce more amendment or see an increase in the consideration of the amendments they offer outside of gaining institutional power. For senators serving without a chairmanship, like Senator Tom Udall (D-NM) and Senator Jeff Flake (R-AZ), it is understandable why they would characterize the chamber as one where it is difficult to promote legislation and participate in an open amendment process.