Justice Souter has tendered his resignation from the U.S. Supreme Court, effective this summer, so the race is on to fill the first U.S. Supreme Court vacancy of the Obama Presidency. Souter is one of the four judges who make up the liberal wing of the U.S. Supreme Court, despite the fact that Souter was appointed by George H.W. Bush, so the balance of power on the court will not be upset by an Obama appointment.
Moreover, given that there will be sixty Democrats in the U.S. Senate when the appointment is voted upon by the Senate, Obama has a free hand to make an appointment without worrying about a Republican led filibuster of an appointee.
The Souter resignation also increases the likely total number of appointments that President Obama will get to make during his term of office. Justice Souter is relatively young and in good health, unlike a number of is peers on the nation's highest court.