"Between 1849 and 1852, (John Archibald Campbell) argued eleven cases in the United States Supreme Court, making such a favorable impression on the justices that, when a vacancy opened in 1852, they unanimously petitioned President Franklin Pierce to name him to fill it. Pierce acquiesced, and Campbell joined the Court in 1853 at the age of only forty-one." --McGinty, Lincoln and the Court, 2008, p. 93.
Here's a friendly reminder that even though a lot of the procedures by which the United States government operates are set out by the Constitution, there is room for the operation of customs and traditions such that what seems unremarkable in one era would be shocking in another. All the Constitution has to say about the appointment of Supreme Court justices is that they are to be nominated by the president with the advice and consent of the senate (Article 2, Section 2). In other words, there is absolutely no reason why, constitutionally speaking, the same process by which Campbell got his seat on the high court in 1852 couldn't also happen today.
But just imagine for a second that this did happen today. There is speculation that John Paul Stevens may be getting ready to resign. Suppose the speculation is accurate and we're about to have a vacancy. Imagine that all eight of the other justices signed a note to President Obama saying that so-and-so is the best man (or woman) to join us on the court, and we respectfully urge you to nominate him. Think that would go over well?
It might be a sad commentary on the politicization of the courts that one's first thought is that this could never happen because there is no way in hell Clarence Thomas and Stephen Breyer would agree on the ideal new colleague. But even if you got past that hurdle, and there was a unanimous judicial recommendation, think of the likely reactions. Some pundits would express outrage at the justices for their audacity, trying to get their two cents in when they are the one branch of the government that is conspicuously left out of the judicial nomination process. Other commentators would point out that if the President did not follow the court's advice, the person Obama ultimately did nominate would be in a very uncomfortable position having to work with colleagues that touted somebody else for the job.
And then what would bloggers, talking heads, and the like have to say about Obama's response to the Court's endorsement of a successor? The President would be in a no-win position. If he gave his approval to the Court's choice, he'd be accused of being a weak executive reduced to rubber stamping a questionable action by another branch of government. On the other hand, if Obama discarded the unanimous recommendation of the Court, some would bellow, "Who does he think he is, not following the advice of eight people who are experts at what makes a good supreme court justice since that's what they themselves are?"
Now just because there is no constitutional reason the selection of a new Supreme Court justice today couldn't go the same route today as it did in 1852, that doesn't mean that what happened with Cambell was a good idea. In fact, I'll go on record that the circumstances behind the Campbell nomination were terrible, largely for the reasons I've sketched above. There's an advantage to a country and a constitution getting a little age on them; as the experiments in democracy have time to simmer it becomes less likely that a bad idea will become an uncontroversial tradition.