“Sonia Sotomayor will turn 70 this June. If she retires this year, Biden will nominate a young and reliably liberal judge to replace her. Republicans do not control the Senate floor and cannot force the seat to be held open like they did when Scalia died. Confirmation of the new justice will be a slam dunk, and liberals will have successfully shored up one of their seats on the court — playing the kind of defense that is smart and prudent when your only hope of controlling the court again relies on both the timing of the deaths or retirements of conservative judges, plus not losing your grip on the three seats you already hold”