The piece by Jeff Rosen that Orin links to below is interesting, and well worth reading, but the part about Obama's philosophy in appointing Justices is, in a word, fanciful. When Obama decided on his first Supreme Court nominee, he wasn't looking for the most distinguished appointment, the nominee most likely to create a new type of liberal judicial paradigm, or, for that matter, a judicial minimalist cognizant of the lessons of the past fifty years as elaborated upon by such brilliant liberal theorists as Jack Balkin, Barry Friedman, and Pamela Karlan. Rather, it's pretty obvious he went for what seemed to be the best political choice: a respected Hispanic woman with a compelling life story.
Sotomayor obviously has far more than the minimal paper qualifications to be a Justice, but no one I've spoken to, or for that matter read in print, has made the case that she is the best nominee to push forward any particular liberal agenda. Indeed, most observers seem to think she is less capable than her primary short-list competitors, and Obama did not have any of the many exceptionally well-qualified white males on that list.
Taking political considerations into account when appointing Justices is hardly unique to Obama. You'd be hard-pressed to find anyone who thinks that Harriett Miers, Clarence Thomas, David Souter, Anthony Kennedy, Sandra Day O'Connor, or John Paul Stevens were the most distinguished candidates available to the presidents who nominated them (and even Justice Scalia was chosen, in part, to woo the ethnic Catholic vote). The past four appointments, two by President Bush and two by President Clinton, were actually unusual historically in that the candidates selected were, in fact, arguably on any reasonable short list for the best available candidates. Selecting a merely excellent or very good candidate for political reasons is a reversion to recent historical norms.
But Rosen's piece reminds of something more broadly applicable to Obama supporters. Many of them seemed to hope and believe that Obama was destined to be not just a standard liberal Democratic president, but in some sense a transformative one, who would reinvent liberalism for the 21st century and bring it back to the political dominance it had between the New Deal and the 1960s. I've seen very little evidence that this is the case; Obama seems to be governing more like a reincarnated Tip O'Neil, sensitive primarily to the concerns of Democrats in Congress and various Democratic or potentially Democratic political constituencies, than like the visionary of liberal dreams. And the Sotomayor appointment is just additional evidence.