Any Republican nominee for the court will be as Federalist-society solid as John Roberts or Samuel Alito.... [A] court in which Breyer and Ginsburg are replaced by nominees from any conceivable Republican president will be a court that rapidly erases their legacies....That's under-analyzed. Is there enough time left to "retire in time"? The new Senate won't be seated until January 2015, but how would it work for the Senate to be dealing with one or two Supreme Court nominees as 33 Senators face reelection and the very question of which party will get control of the Senate is hotly fought? Theoretically, Obama could nominate individuals who would present the Democratic Party in the most favorable light, but what sort of characters would they be? Could Democrats agree, and if not, is their disagreement something that would make Democrats look good in the fall election season?
Ginsburg and Breyer might not prefer a Supreme Court that is highly partisan and ideologically divided, in which retirements are strategic moves. But that's the court they've got. If they care about the principles they've fought for, they should retire in time for confirmation battles this year.
If Obama would be forced to pick innocuous moderates, he might as well wait until after the election and risk having to seek approval from a Senate that contains more Republicans. And I think that the more Republicans end up in the Senate in 2015, the more likely it is that a Democrat will be elected President in 2016, so Ginsburg and Breyer can just as well stay put. Assuming they're plotting this all out politically.