Peter Wehner’s New York Times op-ed “Have Democrats Pulled Too Far Left?” earlier this week might have been the apotheosis of concern-trolling. His claim:

[I]n the last two decades the Democratic Party has moved substantially further to the left than the Republican Party has shifted to the right. On most major issues the Republican Party hasn’t moved very much from where it was during the Gingrich era in the mid-1990s….
For demographic reasons, many Democrats believe that they are riding a tide of presidential inevitability. They may want to rethink that. They are placing a very risky bet that there are virtually no limits to how far left they can go.

That first paragraph falls under the “almost entirely wrong” category. If you look at the standard political science metrics for this sort of thing, “Republicans are now furtherest to the right that they’ve been in 100 years,” as Keith Poole put it (and he would know). Poole is hardly the only political scientist to point this out. Many (though not all) of the examples Wehner gives of the Democrats shifting leftward are on social issues where the entire country has shifted in a more progressive direction. There’s also the fact that Wehner has made a living the past few years begging “people of strong philosophical/conservative convictions… to radiate a temperamental moderation.”

But there are times when a badly flawed essay can nevertheless generate some interesting thoughts. Wehner seems mostly concerned about the presidency, and even Democrats in good standing would acknowledge that: a) Barack Obama is more liberal than Bill Clinton; and b) Hillary Clinton’s initial campaign pronouncements have her moving leftward on a lot of issues. Yes, Republicans have shifted even farther to the right, but the consensus in political science is still that Democrats have shifted to the left over the past few decades.

But here’s the thing: What if, at the presidential level, these party shift towards their respective bases are mutually enabling?

At the presidential level, the general presumption is that the Median Voter Theorem should hold — that is, in order to win, candidates can’t deviate too far from the median voter’s policy preferences, in order to ensure receiving a majority of votes:

This fits the conventional wisdom of the need for major party candidates to gravitate toward the center in the general election.

The thing is, political scientists can think of a lot of ways in which the median voter theorem might not hold. Thirty-five years ago, Thomas Romer and Howard Rosenthal pointed out that agenda-setters could exploit the differences between the median voter’s policy preferences and the actual status quo to articulate a new policy that comes as close as possible to the agenda-setter’s preferences. The key part of their finding is that the farther away the status quo is from the median voter, the more a partisan agenda-setter can propose an alternative that deviates from the center while still attracting a majority of support.

In presidential politics, the agenda-setters who matter are the party activists and funders, and an awful lot of them have more extreme positions than the median voter, or even the median voter within the party. And, as I’ve noted repeatedly in this space, the fierce competition on the GOP side is causing all of the candidates to shift ever rightward on foreign policy and many other issues. But as Romer and Rosenthal would note, the GOP’s sharp shift rightward enables the Democrats to move somewhat leftward while still attracting the median voter.

Conservatives might not like this, so here’s a narrative that might resonate more. If you postulate that President Obama’s policies are to the left of the median voter, then Republicans do not need to articulate perfectly centrist policies — they can articulate proudly conservative policies that are just a little closer to the median than Obama. The problem is that if GOP presidential candidates go too far in outbidding to please party activists, then this allows Clinton or Sen. Bernie Sanders (I-Vt.) to shift even more leftward.

It’s possible that conservative Republicans are betting that the median American voter has also shifted rightward. Maybe that’s true. But the biggest problem with Wehner’s op-ed isn’t that he’s wrong about Democrats; it’s his assumption that Republicans are not shifting rightward. Simply put, in presidential politics, the farther the crop of GOP presidential candidates shifts to the right, the easier it will be for Clinton to shift slightly less to the left and still seem like the more moderate candidate.

This dynamic work in reverse: If Democrats shift too far leftward, it enables the GOP to move even farther right. Which makes me wonder if there’s a Straussian interpretation to Wehner’s op-ed. He’s not concern-trolling; he’s legitimately worried that a leftward-shifting Democratic Party will push the GOP so far rightward that Wehner will start to feel uncomfortable in his own party.