House retirement season seems to be in full swing, particularly on the Republican side of the aisle. Over the past two weeks, six GOP House members have announced they are leaving office, including four members from Texas. In total, 11 House Republicans have said they are not running for reelection, including two members who are seeking higher office: Alabama Rep. Bradley Byrne is running for Senate, and Montana Rep. Greg Gianforte is running for governor. By contrast, only three Democrats have said they are retiring so far in the 2020 cycle.

And given the high number of Republican retirements from the House in 2018 — at least 23, according to our count — which marked the most “pure” GOP retirements (in other words, excluding those who left to seek another office) since the 2008 election, we wanted to better understand what is driving Republican retirements this year. So here’s a look at how the members voted (including how often they were in line with the president’s stated position), the makeup of their districts and the margin by which they won reelection in 2018:

Nine ‘pure’ GOP retirements so far in the 2020 cycle Republicans who declined to seek reelection, excluding those leaving to run for other office, as of Aug. 6, 2019 District Member Trump Score DW-Nominate score Partisan Lean* 2018 vote margin GA-07 Rob Woodall 100.0 0.605 R+17.2 +0.2 TX-23 Will Hurd 51.2 0.295 R+4.3 +0.4 TX-24 Kenny Marchant 95.2 0.602 R+17.3 +3.1 TX-22 Pete Olson 95.0 0.549 R+19.4 +4.9 IN-05 Susan Brooks 95.2 0.362 R+15.3 +13.5 AL-02 Martha Roby 95.2 0.362 R+31.0 +23.0 MI-10 Paul Mitchell 95.3 0.432 R+27.0 +25.3 UT-01 Rob Bishop 97.6 0.536 R+40.5 +36.7 TX-11 Mike Conaway 97.7 0.591 R+64.7 +61.7 Trump Score is just for the 116th Congress. *FiveThirtyEight’s partisan lean metric is the average difference between how a state votes and how the country votes overall, with 2016 presidential election results weighted at 50 percent, 2012 presidential election results weighted at 25 percent and results from elections for the state legislature weighted at 25 percent. Note that the partisan leans in this article were calculated before the 2018 elections; we haven’t calculated FiveThirtyEight partisan leans that incorporate the midterm results yet. Source: ABC News, U.S. House of Representatives, VoteView

As you can see, these retirements have come from very different corners of the GOP. All but one of them has voted overwhelmingly with Trump during the 116th Congress, but the members range from being quite moderate to fairly conservative, based on the ideological measure DW-Nominate. And although the partisan lean of all these districts is at least somewhat Republican, the retirees also experienced a mix of results in 2018, ranging from extremely narrow wins to easy victories. But broadly speaking, these retirements fall into three main groups — those who have disagreed with the president, those who faced tough reelection odds and those who would likely lose their seniority status. Some members, of course, fall into more than one category.

First, there are the four Republicans who have criticized Trump or, at the very least, opposed him on key votes, suggesting a level of discomfort with the direction Trump is taking the GOP. Texas Rep. Will Hurd is the most obvious such case, in that he has the lowest Trump score among the Republicans retiring and the second lowest among Republicans in the 116th Congress. Hurd was one of 14 Republicans who voted to override Trump’s declaration of a national emergency on the U.S.-Mexico border, and was one of just four Republicans who voted in favor of a resolution that condemned Trump’s tweets about four Democratic congresswomen of color as racist. There is also Indiana Rep. Susan Brooks, who is one of the three other Republicans who voted to condemn those tweets. Brooks voted more in line with the president than Hurd, but as the co-chair of the Tuesday Group, a caucus of moderate Republicans in the House, she and other members of that group have had difficulties navigating Trump’s polarizing presidency.

And while Michigan Rep. Paul Mitchell didn’t vote to condemn the president over his tweets, he was openly critical of them. It may have been the last straw for Mitchell, too, as he announced his retirement about a week later, telling Politico that he was tired of the “rhetoric and vitriol.” Lastly, even though Alabama Rep. Martha Roby hasn’t been critical of Trump recently, and has a very pro-Trump voting record overall, she did say she wouldn’t vote for him in 2016 after the release of an Access Hollywood video tape showed Trump talking about groping women. And this hurt her reelection chances: she faced opposition from a write-in candidate in 2016 and had to survive a primary runoff in 2018.

This brings us to our next group of retirements: those who faced tough reelection bids. At least five of the Republicans retiring fall into this category (including Hurd and Roby), but for most of them, the general election looked to be their trouble spot and not the primary. Hurd, in particular, was vulnerable, as his seat is only 4 points more Republican than the country as a whole, according to FiveThirtyEight’s partisan lean metric, and he’s one of only three Republicans in districts Hillary Clinton won in 2016 who didn’t lose their seats in the 2018 midterm elections. Hurd barely held on in 2018, too, winning his seat by just 0.4 points, so he may have decided he didn’t want a rematch against his Democratic opponent, Gina Ortiz Jones, who is running again in 2020. As for the other Republicans in this category, their districts are redder than Hurd’s, but similar to Hurd, they faced close reelection bids in 2018. Georgia Rep. Rob Woodall, for instance, only held onto his seat after a recount. And two other Texas Republicans — Reps. Kenny Marchant and Pete Olson — won reelection in 2018 by fewer than 5 points. There are also signs that the largely suburban districts Marchant, Olson and Woodall represent are moving away from the GOP in the age of Trump, as part of more suburban districts voting Democratic.

As for the other two GOP retirements, they perhaps were unavoidable because of Republican conference rules that do not allow members to lead committees for more than three consecutive terms, unless they get a special waiver (which is rare). That meant the jig was up for both Texas Rep. Mike Conaway and Utah Rep. Rob Bishop, as each was in his third term as a ranking member or chairman (when the GOP had a majority) of his respective committee. In other words, even if Republicans won back the House majority in 2020, Conaway and Bishop wouldn’t become chairmen of the committees where they currently hold the top GOP spots. Given that they both represent safe Republican seats, they weren’t in electoral danger, so they may have just decided it wasn’t worth sticking around any longer.

Of course, these early retirements don’t necessarily signal a wave of future exits. But considering we’re still many months away from passing the deadlines to run for federal office in all 50 states, the retirement train may keep chugging along in the coming weeks. Other rumored potential retirees include veteran members like 17-term Michigan Rep. Fred Upton, who also voted to condemn the president’s tweets. More possible retirees include the two other Republicans holding onto seats Clinton won in 2016 — New York Rep. John Katko and Pennsylvania Rep. Brian Fitzpatrick. In fact, Fitzpatrick, who also voted to condemn Trump’s tweets, already has a prospective primary challenger lining up to take him on for being insufficiently pro-Trump. There’s also the fact that the last time a party flipped the House in a presidential cycle was in 1952. With that history in mind, as well as the misery of minority status in a hyper-partisan atmosphere on Capitol Hill, don’t be shocked if more Republicans decide to exit stage right.