No one is able to be entirely impartial in their opinions, and Supreme Court Justices are no exception. Presidents usually nominate candidates who exhibit the same biases as the President, and Congress usually confirms them based on the congressional makeup at the time.
In the case of President Bush, he nominated conservative candidates, who were confirmed by a conservative Congress. It is reasonable to assume that President Obama will be more liberal in his choices, which will likely be confirmed by the present generally-liberal Congress.
We may expect that Bush's nominees will continue to apply their conservative philosophies to their decisions, and that they will be in some respects opposed by any future appointees from President Obama, and vice versa. In any case, the court and their decisions tend to even out over time.
A president can recommend people who he (or she one day) would think would be best on the supreme court. This, however, does not make it official. The president's choice has to be approved by the Senate in order for the person to become a supreme court justice. That is about it. The president can not interfere in a supreme court case. In fact, if the president does something that is not protected under the Constitution, they will get impeached and removed from office.
A new justice may shift the balance of the Court from conservative to progressive (or vice-versa) if the Court is almost evenly divided and he or she succeeds a justice with opposite -- or more extreme -- ideology. Conservative and liberal justices tend to view the Constitution and its application differently, which affects both legal and social policy.
A president can influence the direction of supreme court decisions by appointing supreme court justices that think the same way he does. For example President Obama appointed Elena Kagan, and Sonia Sotomayor they are more liberal; while President Bush appointed John Roberts a more conservative justice.
Warren led the Court to many decisions that supported liberal principles.
Warren led the Court to many decisions that supported liberal principles.
A justice on the Supreme Court of the United States has no tenure. It is a lifetime appointment. The justice may, however, choose to retire at any time.
The process by which congressional representatives are allocated to states
There are no explicit requirements in the U.S. Constitution for a person to be nominated to become a Supreme Court justice. No age, education, job experience, or citizenship rules exist. In fact, according to the Constitution, a Supreme Court justice does not need to even have a law degree.
Supreme Court Justice
Warren led the Court to many decisions that supported liberal principles.
Warren led the Court to many decisions that supported liberal principles.
Warren led the Court to many decisions that supported liberal principles.
Warren led the Court to many decisions that supported liberal principles.
Warren led the Court to many decisions that supported liberal principles.
Warren led the Court to many decisions that supported liberal principles.
Warren led the Court to many decisions that supported liberal principles.
Chief Justice of the Supreme Court
Warren led the Court to many decisions that supported liberal principles.
Appointments to the Supreme Court of the US are for life.
The US president appoints the justice and the US Senate approves the appointment.