But lets play devils advocate here and say Obama wants to go the max: in that the question is what is the max. The max is actually getting two more members of the court- justice Souter and justice Ginsberg- to step down before the start of the next term in October of this year. Presently the courts term is already halfway through and most of the cases have been heard. In another month the court will be in recess and the only thing happening would be the selecting of clerks for the next term. Thus, within two months the democratic party could begin pressuring the two named justices to step down for age and or health. Thus Obama would then have the ability to nominate three justices, making for five justices appointed by Obama in his presidency. This would not only insure a liberal majority on the court, but one for at least a decade given the ages of the remaining members. It would also insure that when another justice either died or stepped down the odds would be it would be Justice Thomas or the sitting Chief Justice Roberts . Thus if a republican president is in office the new justice wouldn't change the political shape of the court.
Now some would say why would Obama risk having the senate block the nominations until we get say a president Trump in January 2017; If it was blocked the new justices would insure the opposite, a conservative court for the new decade or more. Obama would one take the risk, since the risk is primarily to his own party's reputation and future power. And two having the court down three justices would force the Senate to accept some of the nominees. The court can operate with eight judges, but to start the 2016/2017 term with only six judges would probably have constitutional issues. In the end it would make life more difficult for the Republican majority, which seems to be all Obama ever cares about.