Justice John Paul Stevens is seated at center during a photo session at the Supreme Court. (Credit: Mark Wilson/Getty Images)

Supreme Court Justice John Paul Stevens will step down after more than three decades on the bench, he said Friday, giving President Obama the opportunity to appoint a new member of the court's liberal wing.

Stevens has been hinting he would retire for months. He hired just one clerk for the next term and gave several interviews to national news outlets in which he confirmed he would step down within Obama's term. The anchor of the liberal wing will turn 90 on April 20; he has served since Gerald Ford appointed him in 1975.

Though he is known for his more liberal views, Stevens has for years used his power as the most senior associate justice to try and build consensus against the court's conservative wing. But he has voiced alarm over several decisions of late that he felt went too far; earlier this year, he authored a 90-page dissent to Citizens United v. FEC and took the unusual step of reading from his opinion from the bench.

Stevens' retirement will set off a summer battle between the White House and conservative activists over another high court opening.

Leading contenders for the post are said to include Solicitor General Elena Kagan and Appeals Court judges Diane Wood and Merrick Garland. Already, conservative groups have attempted to attack Kagan for memos she wrote during her time in the Clinton administration, and Republicans have said they will not rule out filibustering a nominee.

If Kagan is Obama's pick, expect quick calls for documents she wrote while serving in the Clinton administration, which are still locked up at Clinton's presidential library.