“…22 In particular, the evidence presented here suggests that we should estimate two separate models: one for votes on Journal 20 Recent works considering the implications of selective pursuit of party discipline in Congress include Sinclair (1998Sinclair ( , 2000, Rohde (2000, 2004), Roberts (2003), Burden and Frisby (2004), Schickler and Wawro (2006), Lebo et al (2007), and Patty (2008). 21 A few examples that have been studied include committee assignments (Leighton and Lopez 2002), staff (Sinclair 1981), opportunities for promotion within the party organization (Loomis 1984), preferential recognition of legislation (Woon 2008), and the opportunity to offer amendments (Sinclair 1983;Bach and Smith 1988;Roberts 2003). 22 For example, consider Groseclose (2000, 2001), Ansolabehere et al (2001), McCarty et al (2001), Roberts (2003Roberts ( , 2007, Krehbiel (2003), and Krehbiel et al (2005), among others.…”