I like James Andrew Miller's op-ed arguing that Obama should promise Hillary Clinton a position on the Supreme Court, if only because it lays bare so innocently the popular wisdom about the role of the court in American politics. On this view, the court's legal function is minimal, perhaps zero; it is really a council of elders who evaluate legislation on policy grounds, or a third house of Congress that retains a right to veto legislation enacted by the other two. It is more important for justices to be able to horse-trade than to engage in legal reasoning (one's experience as a judge is "inconsequential"). The Warren Court's greatness is due to the political skills of its leader, an ex-governor rather than a person distinguished by his legal talents.
Can we justify a third house? In some ways, it is just a throwback to the original vision of the Senate, which was supposed to consist of notables, quasi-aristocrats, who were not directly elected but appointed by other politicians (state legislatures) who were able to recognize their status and talents. The Senate would restrain the excesses of the House, whose members were directly elected by the rabble and thus likely to indulge its crazy populist impulses. Democracy is kept in check in order to ensure that democracy prevails, with the elites acting through their agents (talented and successful members of the ruling class) determining when democracy gets out of hand. (Modern constitutional theorists call this activity ensuring that law complies with the "principles" underlying the Constitution.) When senators became subject to popular vote in 1913, the elites lost an important device for protecting their interests; the Supreme Court has filled this vacuum.
It's not a terribly appealing picture, but it may be the system we have. If so, it makes sense to evaluate potential appointees on purely political grounds—what are their policy preferences, how strong are their political skills, do they reflect the interests of an important constituency? If the choice for Obama is obvious, then so is the choice for McCain. Although President Bush does not have high approval ratings at the moment, and his decision to invade Iraq was questionable, he undeniably has significant political skills, and his policy preferences are well-known and appealing to the Republican base. True, Bush has no legal experience, but, if Miller is right, this is at best a minor consideration, and there is no rule that Supreme Court justices must be lawyers, anyway. Justice Clinton or Justice Bush? That's a choice worth pondering.