... I'm on the political right, but I think liberaltarianism is a healthy, constructive development. If social democracy comes roaring back, as I think is very likely, a renewed liberaltarian liberalism could become the new center or even the new right -- this was roughly the case in Cold War Europe.
I think this is unlikely; I also think that a shift in this direction has the potential to turn out badly for almost everyone involved. Here I'm starting from the premise that American politics has been fitfully sorting itself into a meritocracy-versus-populism dynamic, with one party (the Democrats) dominated by the mass upper class and the other party (the GOP) representing the middle and working-class voters who resent this newish elite, for good reasons and for bad. The European model Reihan gestures at has succeeded - to date - by largely marginalizing the latter temper, with the result that the continent's right-populist types (your Le Pens and your Haiders) are simultaneously more extreme and more powerless than the equivalent figures in the United States. But conservative populism in the United States is way too potent to be marginalized in that fashion, I think - which makes it very hard to imagine a scenario where Lindsey-Wilkinson liberaltarianism becomes the right-of-center counterweight to social democracy, and the voters and interests that currently comprise the base of the Republican Party simply fade away into irrelevance.
What could happen, instead, is a bigger-tent liberalism - somewhat chastened, perhaps, by some big-government failures in the Obama era - that makes libertarian intellectuals feel welcome, engages them in conversations about smarter regulations and more efficient tax policy, and generally woos them away from their culturally-dissonant alliance with people who attend megachurches and Sarah Palin rallies. This would make for a smarter left-of-center in the short run, but I think in the long run it would be pernicious. It would further the Democratic Party's transformation into a closed circle of brainy meritocrats, and push the Republican Party in a yet more anti-intellectual direction. And it would produce an elite consensus more impervious to structural critiques, and a right-wing populism more incapable of providing them. The Democratic Party would hold power more often, and become more sclerotic as a result; the GOP would take office less often, and behave more recklessly on those rare occasions when it did manage to seize the reins of state.
This is obviously a political gloss on what is essentially an intellectual project, and I know Will, like many libertarians I admire, prides himself on not thinking in terms of partisanship. But for anyone who cares about political outcomes, I think it's important to consider the correlation of forces when you set out on ideological projects - especially in a country where the two-party structure has been as durable as it's been in ours. I understand the impulse for smart, independent-minded libertarians to flee what seems like an increasingly anti-intellectual American Right and seek conversations and alliances with the friendlier parts of the left-of-center. But the vacuum on the Right also militates in favor of smart, idiosyncratic thinkers trying to fill it, instead of fighting for a seat at the crowded liberal table. That doesn't mean registering as a Republican, attending CPAC, or casting a vote for McCain-Palin (or the next iteration thereof). But it means being open to the possibility that the old fusionism, battered and bruised as it is, may still hold as much promise for the advancement of libertarian policy goals as "liberaltarianism" ever will. I'm sure that the right-of-center conversation would be smarter, richer and better off the more a Will Wilkinson or a Brink Lindsey were involved in it - and that goes for your Tyler Cowens and Megan McArdles as well. And I'm pretty sure that the country would be better off as well.