Something unexpected and unusual happened in the House on Thursday: The two parties agreed.

On two votes, H.Res 173 and H.R. 2 — the so-called "doc fix" — an overwhelming majority of the House voted in support. It's not uncommon that the House votes unanimously on an issue, but heavy-but-not-total support seems like it's probably uncommon, especially in our modern, polarized era.

And in fact, it is. Using data from GovTrack, we pulled vote data from the House and Senate since the 93rd Congress. We took out all of the "present" votes, and excluded any vote that didn't include 400 members of the House or 80 of the Senate. The curve looks like this, running from 0 percent support at left to 99 percent support at far right. (We excluded 100 percent votes, since those skew the scale.) Anything in the middle indicates a more contentious vote.

Thursday's two votes fell on the bars that are lighter colored; the "doc fix" came in at 91 percent, the lighter bar that's further to the left.

Notice where 91 percent falls — in that valley between the frequent just-over-50-percent votes and the frequent almost-everyone-agrees. It's not a common margin of support!

Particularly these days. In the 113th Congress, the balance was skewed heavily toward the center of the chart, versus either edge where there's more agreement.

That is more noticeable when you look at groupings of Congresses. If we compare the last five to the first five in our data set (which covered 1973 to 1982), you can see that there have been more votes, more centered around the contentious center of the results range.

So when we marvel at what happened in the House on Thursday, it's not without cause. Congress has been deeply contentious of late. Comity is something we've learned not to expect.