President Barack Obama's selection of Judge Sonia Sotomayor to replace retiring Supreme Court justice David Souter is a gift to Republicans - but not to the law.

The essence of the rule of law is that identity doesn't matter. The law means the same thing regardless of the identity of people applying the law or subject to it. We don't have one law for Jews and another for Catholics, one for Italian-Americans and another for Hispanic-Americans. We don't need to know who the judge is to know what the law is.

Judge Sotomayor's nomination is predicated on almost exactly the opposite understanding of what law is and should be, of what matters in our judges and their decisions. But the defects of the nomination - probably not sufficient to derail its confirmation by a heavily Democratic Senate - are enough to give Republicans a glimmer of hope.

Presidents always vow to pick Supreme Court nominees who are accomplished jurists or scholars with strong intellects, deep understanding of the law, abiding respect for the rule of law, and the capacity to explain clearly what the law means. Justices Scalia and Breyer, to pick two current and often opposed members of the bench, clearly fit that bill. So do several people rumored to have been on the President's short list for this nomination.

Alternatively, Presidents can pick nominees whose appeal lies elsewhere, in attributes that yield political advantage to the president. Many presidents, liberal and conservative alike, have found that temptation irresistible. President Obama apparently did as well, picking a nominee less for her intellect, her understanding of the law, or her facility for interpreting and explaining the law than on her identity. Worse, he picked someone who sees identity as important to deciding what the law is, how it applies, and who wins and loses.

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Judge Sotomayor attended prestigious schools (Princeton, Yale Law), did well, achieved professional milestones as a prosecutor, district judge, and court of appeals judge, and became well enough known to be widely touted as a potential Supreme Court appointment. She isn't seen within the profession as brilliant, a creative legal thinker, especially able at crafting legal decisions, a master of legal analysis, or exposition. But she's competent enough not to be lumped in with the likes of G. Harold Carswell, the Nixon nominee defended on the ground that people who are mediocre deserve representation on the Supreme Court.

Her appointment, however, is transparently based on a very different calculation from her professional qualifications. Judge Sotomayor is, in the colloquial parlance, a two-fer. She's a Hispanic woman. Her appointment appeals to two major constituencies for Democrats. And having the first Hispanic Supreme Court justice would be a real source of pride for Hispanic-Americans, a large and growing bloc of votes. She may not be as well-regarded within the legal profession as, say, Elena Kagan (Solicitor General and former Harvard Law dean) or Diane Wood (judge on the Seventh Circuit of the U.S. Court of Appeals and former University of Chicago Law professor), but she checks off two boxes.

Ordinary partisan politics says this is a smart move - for an ordinary partisan politician. The President wants us to imagine that he's above that, but it's hard to blame him for wanting to please Party faithful.

Liberal interest groups - which often push for interpretations of law less bound by text and more conscious of race, gender, and ethnicity - will applaud the appointment. Judge Sotomayor has said she believes appellate judges "make policy," though she quickly added that she knew her comments were being recorded so she probably shouldn't say that - not the most convincing disclaimer. She also said that she believes her identity makes her different from other judges, that a Latina woman naturally sees the law differently from white males and reaches better decisions.

For her, identity of those subject to the law matters as well. Her decision in Ricci v. DeStefano, summarily upheld race-conscious changes to tests for advancement within the New Haven Fire Department. A white firefighter took time off to study for the advancement test, spent thousands of dollars of his own money, and overcame a learning disability to score among the top candidates, but (along with the other successful candidates) was denied promotion when it appeared too few African-Americans scored well on a test that was designed and checked in advance to be both effective and non-discriminatory. The result in Ricci makes sense only if racial identity is critical to picking fire captains and lieutenants - if it matters more to have a certain percentage of African-Americans than to have people who know what to do around a fire.

To be fair, while Ricci was criticized by another Hispanic Clinton appointee to the Second Circuit as perfunctory and improper, the Supreme Court's precedents on race-conscious decision-making aren't a model of clarity. But Judge Sotomayor won't likely be invoking the current Supreme Court as the touchstone - after all she has an almost perfect record of reversal by the High Court (five times in six tries, and her reasoning was criticized in the sixth).

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Republicans will be gnashing teeth for a long time reading Justice Sotomayor's decisions if she gets onto the Court. And those who care about the rule of law will be appalled by at least some of what she says and does. But there's a silver lining or two here as well. For one thing, Judge Sotomayor is unlikely to be more than a single vote - someone as far from most other justices in craftsmanship and as abrasive as she is won't have much impact on her colleagues' decisions.

And the nomination just might peel away a little Teflon from a very Teflon President. The decision to nominate Judge Sotomayor will mark the time President Obama lost the pretense of being above and beyond partisan norms. That could help Republicans in the next round of elections. Sadly, it will leave the law less certain, less neutral, and less tied to the sources of meaning critical to the rule of law. Which makes this silver lining tarnished from the start.