The aim of this paper is to understand how the behaviour of deputies and senators is structured on roll calls. It is generally assumed that the distribution of revealed preferences follows a one-dimensional structure characterised by the conflict between government and opposition (Leoni 2002; Zucco Jr. & Lauderdale 2011; Zucco Jr. 2009). The studies that suggest this conclusion analyse the behaviour of deputies in the Chamber’s plenary sessions and extrapolate their conclusions to the National Congress, although without taking into account the possible specificities of the Federal Senate. Thus, our first concern is to introduce the Senate into the analysis so as to assess whether or not this legislative house may also be characterised as one-dimensional and if, like the Chamber, the distribution of parliamentarians in this space is characterised by the government-opposition divide. The second question is that, does a party’s formal entry into or exit from the coalition generate a change in the behaviour of parliamentarians? Unlike the first question ˗ whose answer is intuitive ˗ in this respect, a party’s entry into or exit from the coalition does not generate a change in the behaviour of parliamentarians.
