WASHINGTON - For most presidents, choosing a Supreme Court nominee is a puzzle. For President Barack Obama, the chance to pick a successor to Justice Antonin Scalia is even more complicated.

As the White House carries out a rare election-year search for a nominee, the president's lawyers and top advisers are sorting through a tangled web of political factors.

A smart pick and nomination strategy could determine whether Obama gets to reshape the highest court for the next generation. The wrong pick could cede that opportunity to his successor.

For Obama, the clock is ticking. The sooner he picks a name, the longer he has to try to force the Republican-led Senate to hold a vote.

The White House says the president will use the same criteria he used when he nominated Sonia Sotomayor, who became the first Hispanic on the court, and then-Solicitor General Elena Kagan to the court.