I take Scalia, Thomas, and Rehnquist to be the three conservatives on the Court (keeping in mind that they do not, of course, always agree, and that when they do agree they are not always right). If Roberts would be another conservative–even if he would be more like Rehnquist than like Scalia and Thomas–the conservatives would still be one vote shy of a majority. Assuming that the next three vacancies are Rehnquist, Stevens, and Ginsburg, conservatives would have to get conservatives to replace two of the three to have a majority. Lest anyone get carried away–not that I’m seeing much evidence of that–that’s an uphill climb.