Heather Gerken has written this piece for Legal Times. I’d be interested to hear from Heather if she believes that the Carter-Baker commission played this kind of “shadow” role for election administration reform, and if not, how do we ensure that shadow groups are fairly composed and make good decisions.
UPDATE: Heather Gerken responds to my query:

Great question, Rick. In my view, the prominent role that the Carter-Baker Commission played in the Supreme Court’s voter i.d. decision offers two important lessons about shadow institutions. First, it makes clear just how powerful the decision of a shadow commission can be. The Justices were plainly on the hunt for a neutral metric to evaluate the Indiana law. In the eyes of Justices Stevens and Breyer, at least, the Carter-Baker Commission offered just such a metric, and they therefore deferred to it. This is precisely the dynamic I would expect should Ned Foley’s amicus court or my shadow districting commissions be created. People need a baseline to evaluate a decision, and a shadow institution provides it.
Second, the Carter-Baker Commission confirms how important it is for shadow institutions to be composed of nonpartisan experts. (I know, of course, that no one is truly “nonpartisan,” but surely most would concede that we’re dealing with a sliding scale here). Carter and Baker are not experts, nor are they politically neutral. The position the Commission took on voter i.d. is exactly what one would expect from a bipartisan decisionmaking body — an obviously political compromise that lies roughly in the middle of the positions that the political parties have taken on this issue. While I would expect better from a truly nonpartisan body of experts, I will say this. For all if its flaws, the Carter-Baker Commission’s compromise was still superior to what the ruthlessly partisan Indiana legislature passed, a fact that Justices Souter and Breyer used to great effect in their dissents.