The buzz about Obama's nominee for the Supreme Court is that her diverse life background will add an important perspective to the deliberations of the nation's highest judicial body. This may or may not be true, but it is also partially irrelevant--this is a choice driven to gain the votes of a particular demographic.
But why do people keep assuming that high-profile minority appointments will translate into political gains? The experience of the Bush Administration--which had posts given to the likes of Alberto Gonzalez and Colin Powell--comes to mind. It's not as if Clarence Thomas, Antonin Scalia, or Ruth Ginsburg brought in their respective demographics into either party. Voters simply don't make their decisions based on these types of issues--often, they are not even aware.
But the cost of going with the best jurist who is a female Hispanic, rather than the most talented legal theorist, will be felt in the coming years. Had Obama went with an intellectual hotshot, one who could rival Roberts and Scalia by establishing a liberal counterweight, and who could woo the centrists through competent jurisprudence, he could drastically change the temperature of the Supreme Court, even as the executive and legislature have gone through major political shifts. This is the stuff of realignment.
This appointment is symptomatic of the broader problem of short-term politics. Politicians often seek to dominate the short-term news cycle, and gain the approval of the heads of interest groups. But that's not what voters care about. Throw away the weekly opinion polls, narrowly targeted policies, and stop talking to union bosses and teachers unions. Focus entirely on offering good governance. If employment is high, and inflation low--Obama will win a second term, no matter who his nominees are.