Since Woodrow Wilson's (1885) analysis of Congress, researchers assumed that members of Congress look to one another for information, cues, and advice on unfamiliar policy areas. The amount of time and effort that each legislator and their staffers would have to put in to make all of these voting decisions would be insurmountable. Fellow legislators are a resource to turn to for guidance or assistance. Legislators are able to influence their colleagues above and beyond each of their individual preferences. The members of Congress that are most influential will not necessarily be the same for every bill. The significant legislators may be one's co-partisans and the party leadership or they may be a group of legislators with whom they share a common interest. Spatial analysis allows researchers to look more explicitly at the relationships between legislators and their colleagues.
I use spatial probit and a spatial duration model to study these issues by examining the factors that influence voting decisions and the timing of position announcements. I look at a variety of different policy areas, including foreign policy, education, and agriculture, over an extensive time period (1933-2014) to test which relationships are most influential on their decisions. I study the interdependence between three different relationships, same party, state delegation, and ideological similarity, and hypothesize that these ties will lead legislators to behave more similarly. The use of the spatial analysis provides an opportunity to test these relationships and see if even after controlling for other influences there is dependence between legislators. In my research, I find that legislators are interdependent regardless of their individual characteristics. When I analyze voting behavior, legislators' behave similarly from one another across all three relationships above and beyond what we would expect given their personal preferences. These positive findings do not hold when I study the timing of position announcements where legislators behave dissimilarly from one another when interdependence exists. The study, overall, suggests that legislative ties are especially important in explaining voting behavior and that it is critical to account for these relationships.