What House Republicans had hoped to do on Tuesday evening was to impeach Homeland Security Secretary Alejandro Mayorkas, sending a message to the Biden administration (and general election voters) about how seriously they took the border. The caucus had been building to this for months, with multiple hearings and countless media interviews centered on Mayorkas and his purported mishandling of his position.

Then it was time for the House to consider the articles of impeachment — and Republicans didn’t have the votes. A handful of defections from within the party and bad counting on the part of Republican leaders left the caucus scrambling; Rep. Blake D. Moore (R-Utah) had to flip his vote so that his party would be able to bring the impeachment effort to another vote in the future.

It was a debacle. And it was entirely in keeping with the House Republican majority since January 2023.

There are several reasons that the Republican caucus has proved unusually incapable of getting things done. But before we evaluate those reasons, let’s validate that assertion of incapability. Data from GovTrack indicates that the 118th Congress has enacted about 7 percent of the legislation that congresses have enacted on average since the 93rd, back in 1973 and 1974.

In fairness, this Congress is not yet over. The House and the Senate have another 10 months or so to pass legislation. But even if Congress enacts twice as much legislation over the rest of the session as it has since January 2023, the 118th Congress will still end with only a third of the number of laws enacted during the 117th.

So why is this happening? Setting aside that the Senate is controlled by Democrats — lowering the likelihood that both chambers will pass agreed-upon legislation — there are three central challenges.

The first is that the Republican caucus has that slim majority. There are seven more Republicans than Democrats, meaning that Speaker Mike Johnson (R-La.) can only lose three votes without losing his majority. On Mayorkas, he lost those three votes — and he was missing House Majority Leader Steve Scalise (R-La.).

But that overlaps with the second reason: Republican legislators are more likely to defect from the party minority.

To measure this, I took data on every roll-call vote (that is, a vote in which legislators recorded their choice) since the 108th Congress. On each vote, a plurality of each party’s caucus supported one position and, usually, some members disagreed. We can generate a percentage as follows: If there are 10 Republicans and nine vote for the caucus’s majority position, that means a 90 percent agreement within the party.

Looking at that data, you can see that the average support from the Republican caucus for the majority position has been less than 90 percent since the 116th Congress in 2019 and 2020. (This is indicated by the black lines on the chart below.) Among the Democrats, there’s much more consensus: On average, the party’s caucus has had 96 percent of its votes cast with the majority position over that same period.

You can also see how often the Republican caucus has seen even larger defections from the majority with the gray-shaded sections. In the 118th Congress, nearly 9 in 10 roll-call votes for the Democrats have had at least 90 percent of the caucus on board. For the Republicans, only a bit over half have had that level of unity.

The outlier here is actually the Democrats, not the Republicans. Party caucuses averaged 89 percent agreement in votes from the 108th to 115th caucuses — not much higher than where the Republicans are now. But the Democrats’ unanimity makes it more important for Republicans to be similarly unified, which they aren’t.

This is partly because there are at least two distinct segments of the Republican caucus, one on the far-right and one on the near-right. This has been most apparent in the caucus’s multiple efforts to elect a speaker; the more-extreme segment was more likely to oppose the candidacy of Kevin McCarthy in January 2023 and the less-extreme part more likely to oppose the candidacy of Rep. Jim Jordan (R-Ohio) last fall.

This brings us to the third reason that House Republicans are having so much trouble: They’re under pressure, especially from the far right, to take more difficult votes.

The Mayorkas impeachment is a good example. It’s an extreme response to immigration issues that built up a head of steam in the right-wing media, a world to which the caucus’s right-most fringe is particularly sensitive. So the articles of impeachment came forward — and less-extreme legislators skeptical of the idea balked.

None of these factors means that the caucus can’t get anything done. After all, they came within Scalise’s vote of impeaching Mayorkas. They still may.

But it does explain why, so far, they haven’t been able to do much.