Dana, Adam, and Ezra have already identified one likely line of argument against any non-white male Obama nominee, i.e. the idiotic argument that any Democratic appointee who isn't a white male must ipso facto not be the "most qualified" Supreme Court candidate (whatever this could possibly mean). A couple more of the potential arguments can be found in this post from Ed Whelan. First, we have the tired claims that anybody whose interpretation of the Constitution differs from Whelan's is a "judicial activist" who isn't sufficiently "dispassionate." Such arguments have always been vacuous and, less than a decade after Bush v. Gore, have become self-parody. (Although it will be interesting to see how many reporters and centrist pundits -- apparently having yet to be informed of Earl Warren's death nearly four decades after the fact -- go along with the conflation of "activist" with "liberal.")
Another strategy Whelan uses is the parade of "horribles." Whelan asserts that Obama's nominee might provide the fifth vote for such holdings as "stripping 'under God' out of the Pledge of Allegiance" and "the invention of a constitutional right to human cloning." Given that the current number of votes for these outcomes on the Supreme Court is zero, I'm not sure how this will work. But I'm pretty excited that Obama's nominee will apparently be a super-justice who gets five votes to herself.
Another approach may be what can only be called comic relief. Michelle Malkin's "legal sources," for example, assert that "it is also unclear that a Justice Kagan would be an adequately independent check on executive excesses." Yes, if there's anything that the Court's conservative members are known for, it's their strong belief in checking the president's power. They also assert about Sonia Sotomayor that "lawyers who have appeared before her have described her as a 'bully'" who "does not have a very good temperament," and who "abuses lawyers" with "inappropriate outbursts." I look forward to Malkin's immediate demand that Justice Antonin Scalia resign from the bench...
--Scott Lemieux