Sonia Sotomayor and Samuel Alito had virtually identical formal credentials—Princeton undergrads, Yale Law School, long careers on the federal bench. But Alito was treated with great deference by the press, and even opponents of his nomination based their arguments on his consistently reactionary judicial philosophy rather than suggesting that he wasn't "qualified." Sotomayor, conversely, was subject to repeated arguments that she lacked the intellectual abilities to serve on the Supreme Court. In a particular low point, immediately before Sotomayor's nomination The New Republic's Jeffrey Rosen published a disgraceful article full of anonymous critics engaging in sexist attacks on Sotomayor that can't even be called "veiled"—aggressive questioning that would be considered charming if it came from Antonin Scalia showed that she didn't have the appropriate temperament, that the distinguished Yale Law-educated jurist lacked the intellect to be on the Supreme Court, etc.
Needless to say, the sexist double standards applied to Sotomayor aren't just confined to Supreme Court nominees. As shown by an important new paper by Rebecca Gill, a professor of political science at UNLV, sexism and racism (whether conscious or unconscious) appear to play a substantial role in evaluating judges at the state level as well. Following up on earlier work published in the Law & Society Review, Gill's paper looks at the "Judicial Performance Evaluations" that, according to guidelines established by the American Bar Association, that allow lawyers to assess the performance of judges. This information is then provided to voters and can play a role in judicial elections. However, these evaluations are anonymous and lawyers do not have to prove that they have actually argued a case in front of a judge they're evaluating, so their value is not self-evident. What Gill's analysis found is disturbing. As you can see if you scroll down to Table Four in Gill's paper, with the exception of being accused of scandalous behavior none of the factors that could be expected to contribute to stronger judicial performance—judicial experience, educational background, reversal rates—had a significant effect on the performance evaluations. What did have a strong impact on judge evaluation was the race and gender of the judge, both of which had a strong negative correlation with assessment of their judicial ability. Being a woman or person of color hurts your judicial evaluations more than having a reported scandal.
The double standards applied to Sotomayor were far from anomalous. Things are not quite as bad as when Sandra Day O'Connor graduated third from her class at Stanford and was offered nothing but secretarial work—but a lot of assumptions about women and racial minorities being inherently less qualified to be judges clearly persists.