Senator Strange will not be back in Washington next year. Senator Corker will not be here in 2019. And Senator Flake may not be either.

What do these three GOP Senators have in common?

The primary system. Senator Strange was beaten by it. Senator Corker got scared into retirement by it. And Senator Flake is gearing up to be challenged by it.

As Anthony King wrote 20 years ago in his wonderful article The Vulnerable American Politician, the U.S. electoral system is an outlier among democracies in creating unsafe incumbent politicians. American legislators face more elections than politicians in other countries, they are forced to raise their own money for campaigns, they must succumb to nomination challenges via ballot, and the weak American parties provide them little cover from constituents angry at their policy choices. King described many of the well-known consequences of this reality: members are hyperresponsive to consituents, have short 2-year time horizons for policy decisions, spend lots of time raising money, and often bring a risk-averse outlook toward tough policy decisions.

What is fascinating in the contemporary political environment is that many members of Congress occupy districts where their main vulnerability is not in the general election, but in the primary. The rise of so-called “safe seats” is a well identified trend going back over a generation; Mayhew identified his vanishing marginals in 1974. But the safe seat designation is a misnomer; the seats are only safe in the general election. Members are secure only to the degree they can forestall a credible primary challenger on the left (if they are a Democrat) or the right (if they are a Republican). And so Members vulnerable to these challenges spend a lot of time positioning themselves as solid liberals and conservatives.

The interesting developments are on the right. Since 2010, conservative politicians have increasingly run and won elections by tapping into voter and activist anti-Washington and anti-establishment sentiment in these safe districts. Sometimes they have defeated incumbents for nominations and won general elections (Mike Lee; probably Roy Moore); other times they have won open-seat primaries just to lose to Democrats in otherwise winnable seats (O’Donnell in Delaware; Angle in Nevada); sometimes they have unseated incumbents in primaries and gone on to lose general elections (Mourdock over Lugar in Indiana). The threat of such a challenge may also scare incumbents into retirement, who would rather go out on their own terms than face an embarrassing primary loss.

As the GOP base moves further to the right in its anti-Washington and anti-establishment thinking, the trend appears to be accelerating. After the victory by Moore over Strange this week, Steve Bannon has pledged to begin recruiting primary challengers across the country, in an effort unseat GOP incumbents who are not sufficiently populist or anti-establishment. In addition to Corker’s seat and the challenge to Flake, this may add Senator Wicker (MS) to the target list and a host of moderate House Republicans.

The dilemma for many incumbent GOP legislators is stark. Part of the attack upon them is that they are insufficiently anti-establishment, evidenced by the fact that they are too cozy with the congressional leaders. But defining the congressional leadership as tantamout to “the establisment” eates an intractable problem under the populist never-compromise ideology of the far right. Leaders in Washington *have* to compromise, because our system of government demands it; the only other choice is to get nothing done. So each GOP incumbent is in the uncomfortable spot of potentially facing a primary challenger who will accuse them of cozying up to the leadership and selling out to the establishment, all the while knowing that the only choices they have in DC are to either work with the leadership to accomplish things or join the chorus of anti-establishment attacks that make headlines but accomplish little concrete policy.

I was discussing this (in more simple terms) with my 9-year old last night, and it dawned on her that there’s a serious recursive problem here. You can win a primary and defeat an incumbent, but the moment you attempt to work with the leadership, you will yourself be exposed to a primary challenge on *your* right, as you have now become a compromising member of the establishment. To some degree, this is true almost regardless of ideology; once the leadership in Washington has become the hated establishment, it becomes in some ways its own substitute for ideology. The deals themselves are the enemy.

Of course, this is even more plainly true for the leaders, who are stuck in a similar game with their conferences. You can remove them (Boehner; maybe Ryan and McConnell), but anyone who takes the job will instantly be forced to make deals and become part of the establishment. And so you have the recursive problem facing both sides of the GOP right now; neither the leaders or followers can cut deals in Washington without exposing themselves to someone’s wrath. The rank-and-file are scared of the primary challengers, and the leaders are scared of the rank-and-file.

There’s an old belief that the world is flat, and lays on the back of a turtle, who himself is standing on a larger turtle. When the curious student asks the teacher what the larger turtle is standing on, he is met with a terse response. “It’s turtles, all the way down.” As we stand at the beginning of the 2018 primary preseason, you may be tempted to ask a similar question to the one my daughter posed last night. Where does this end?

Quite possibly, it’s primaries, all the way down.