Caucuses are full of actual people who are worried about representing^W being reelected in vastly different districts. Party leadership can never rely on gettin

Caucuses are full of actual people who are worried about representing^W being reelected in vastly different districts. Party leadership can never rely on getting every vote; this is why whips were invented. In the case above, there was zero bipartisan cooperation past the original proposal, so the individual senators really mattered.