For the past two decades, one of the least understood but most important unwritten job requirements for congressional leaders has been to protect their members from difficult and potentially politically costly votes, either in committee or on the floor. Some of the most pressing policy issues of the day are never voted on or are so diluted that one would be hard-pressed to use voting records to nail down how any member feels about anything of real consequence.

Senate Majority Leader Harry Reid and House Speaker John Boehner both understand that sparing their members from casting difficult votes is now part of their jobs—and, in their caucus members’ eyes, a very important part. Maybe it’s a vote that would force some members to choose between their party’s base and swing voters, or maybe it’s one that would alienate a key constituency: Avoidance is preferred to pain. Even if many in the party are chomping at the bit to take on an issue, they usually end up deferring to party leaders who will sideline a vote if it endangers enough members, particularly if a party’s majority in a chamber is on the line.

In the old days, senators would disdainfully look down on the House, the “lower body,” in part because the House Rules Committee so thoroughly regulated floor debates and amendments. In recent years, however, the Senate has grown more restricted as constant threats of filibuster prevent consideration of controversial legislation. These days, the Senate majority leader often resorts to a tactic employed by the late Sen. Robert Byrd and former Sen. Bob Dole called “filling the amendment tree,” which prevents the minority from offering troublesome amendments. It’s now commonplace for House members to refer to the Senate as a legislative cemetery, a place where bills go to die.