Any successful nominee should possess both the temperament to interpret the law and the wisdom to do so fairly. The next Supreme Court Justice should have a record of protecting individual rights and a strong willingness to put aside any political agenda.
I like to imagine, as a thought experiment, the day, perhaps not too far off, when a Republican president nominates a Supreme Court Justice married to someone of the same sex, maybe even with the sanction of 'orthodox' theology - with that gay Supreme Court justice casting the deciding vote that finally overturns 'Roe vs. Wade.' It could happen.
When you have incidences like the Trayvon Martin verdict, the erosion of certain fundamental rights like voting, it just reminds us that we're always one Supreme Court justice vote away from losing the progress that has been made.
Finally, a good prosecutor knows that her job is to enforce the law without fear or favor. Likewise, a Supreme Court Justice must interpret the laws without fear or favor.
There is no more moving a professional relationship than that between a law clerk and a Supreme Court justice. As a place to work, the court is unique in its intimacy and intensity.