Andrew Hyman of ConfirmThem.com writes to note that he has commented on this issue before, and raised the very good additional objection that the advocates of giving the District of Columbia representation in the House have to get around this language in the Fourteenth Amendment: “Representatives shall be apportioned among the several States according to their respective numbers, counting the whole number of persons in each State, excluding Indians not taxed.” And as long as D.C. isn’t a state, well, you get the rest.
Andrew’s comment also informed me that another legal scholar who I would have thought knew better than to support this idea, does in fact support it: Viet Dinh, formerly of the Bush Justice Department. Eugene Volokh also weighed in on this issue a few months ago, reviewing Dinh’s views and Ken Starr’s, and pronouncing himself unpersuaded.