Adam , I meant neither to endorse "a longtime practitioner" nor to exclude law professors or sitting judges from consideration for court vacancies. Persons holding any of these positions may qualify as "lawyer's lawyers" or, indeed, "judge's judges."
Fitting those two labels is in part a matter of experience. But it is more importantly a matter of temperament—a matter both of the means a person employs to solve a question of law and the manner in which the person explains that resolution in an opinion. There are longtime practitioners who are not lawyer's lawyers. There are members of the bench who are not judge's judges. There are practitioners who display judicial temperament even though they have never donned black robes. Various law professors fit various categories.
The Stevens example is set forth simply to provide food for thought about what may happen when a president gives certain qualities priority over partisan political concerns.
With regard to your specific references, I am not persuaded that the nomination of John G. Roberts Jr. , for whom I have great respect, serves as an equivalent example. His intellect, wit, and dignity indeed are welcome additions to the court. But the man who is now chief justice of the United States served in the executive branch, and that experience alone sets him apart from Stevens. Accounts like those in Jeffrey Toobin 's The Nine (2007), moreover, suggest a greater ideological bent than was evident in Roberts' nomination hearings; and correct or not, a sense among some Democrats that there was such a bent no doubt underlay the "nay" votes mentioned in the Los Angeles Times article that spurred this blogthread. (This too sets Roberts apart from Stevens: 1975 predictions by U.S. Rep. Bella Abzug , D-N.Y., and the National Organization for Women that Stevens would do harm to women's rights did not convince a single senator to vote against him.) Finally, not all the chief's opinions have adhered to the " balls and strikes " metaphor he famously pitched when seeking nomination; last term's Seattle School District and this term's Medellín may be said to have set precedent as much or more than they followed it.
Though we may exercise a blogger's prerogative of contributing our two cents, we cannot be certain of what either presumptive presidential nominee will do unless and until he has the power actually to make a judicial selection.