I want to spend another moment on this great graph Todd Lindeman worked up for my column on the constitutionality of the filibuster.

(Graph: Todd Lindeman; Data: Senate.gov)

What you’re seeing here are the number of “cloture” motions in every congressional session since 1919. Cloture is the procedure used to break a filibuster. Between 1919 and 1975, a successful cloture motion required two-thirds of the Senate. Today, it requires three-fifths, or, in cases where all 100 senators are present and voting, 60 votes. As you can see, the majority is having to try and break many, many, many more filibusters than ever before.

This is an imperfect measure. On the one hand, it’s susceptible to changes in congressional strategy: If the majority begins trying to break the filibuster more often, you could see more cloture votes, even though the filibuster isn’t actually being used any more frequently. On the other side, it misses the many, many, many filibusters that never receive a cloture vote, either because the majority decides that a cloture vote is too time-consuming — simply holding a cloture vote takes about 30 hours of floor time — or because they won’t win it.

That said, it is, at least, a relatively consistent measure, and it’s the best one we have. And most observers agree that its basic point is correct: We’re seeing many more filibusters today than we ever did before. But I actually think that’s the wrong way to think about it.

The issue today isn’t that we see 50, or 100, or 150 filibusters. It’s that the filibuster is a constant where it used to be a rarity. Indeed, it shouldn’t even be called “the filibuster”: It has nothing to do with talking, or holding the floor. It should be called the 60-vote requirement. It applies to everything now even when the minority does not specifically choose to invoke it. There are no longer, to my knowledge, categories of bills that don’t get filibustered because such things are simply not done, though there are bills that the minority chooses not to invoke their 60-vote option on. That’s why Harry Reid says things like “60 votes are required for just about everything,” though there are a small number of bills where the majority uses the budget reconciliation process to short-circuit the 60-vote requirement.

An interesting implication of this graph: The filibuster has become more common even as it’s become easier to break. Until 1917, the filibuster couldn’t be stopped. And until 1975, you needed two-thirds of the Senate, rather than three-fifths. So as it’s become less powerful, it’s become more common. What that means is that the rise of the filibuster is largely about “norms” in the Senate. It didn’t become more effective and thus more popular. It actually became less effective, but parties chose to use it more.

There’s an interesting question around exactly when this change in norms happened. If you look at the graph, you have three major moments of discontinuity. One, around 1972, that appears to provoke reform of the filibuster rules so cloture is easier to achieve. Another, in the early 1990s, that seems covers the latter half of George H.W. Bush’s administration and the beginning of Bill Clinton’s presidency. And then the practice absolutely skyrockets when Barack Obama takes office.

We can argue about why there were these jumps. But their long-term effect seems to be to raise the bar permanently. Every time filibustering becomes much more common, it pretty much remains at that level, even as Congress and the White House changes hands. So the filibuster becomes more common under Bill Clinton, but remains almost that common under George W. Bush.

For more on the filibuster, here’s Greg Koger making the case that it’s clearly constitutional. Jonathan Bernstein agrees with him. Here’s more from Common Cause on their lawsuit.