President Barack Obama announced Friday that Supreme Court Justice David Souter has informed the White House he is retiring this summer, formally kicking off what could be the biggest political test of Obama’s young presidency.

In a surprise visit to the White House briefing room, Obama pledged to wage a rigorous process for choosing his replacement, even as he reiterated his desire to tap a nominee who will use “empathy— in ruling from the bench.

Obama appeared careful to portray himself as being open minded as he approaches the task. While saying his choice must have empathy, Obama also said he was looking for a “sharp and independent mind.—

The president suggested he wanted someone with practical knowledge of the law’s effects on everyday people, someone who is “not about abstract laws in a casebook.—

Obama pledged to talk to both Democrats and Republicans about his possible pick, saying he will consult with lawmakers of a range of ideologies. He said he hoped to have a justice in place by the time the Court convenes the first week in October.

White House Press Secretary RobertGibbs said Obama would begin talking to lawmakers of both parties “somewhat quickly,— indicating it was likely a nominee would be sent up to the Senate by the end of July.

Judiciary Chairman Patrick Leahy (D-Vt.) praised Souter’s tenure on the court and urged his colleagues to work together during the nomination process. He said he was confident Obama would consult with Members on his selection.

“I know that as President Obama selects a nominee to replace Justice Souter, he will continue to consult with Senators from both sides of the aisle as he has this year with so many nominations. In exercising their important roles in the confirmation of the next Supreme Court justice, I hope that all Senators will take this opportunity to unify around the shared constitutional values that will define Justice Souter’s legacy on the Court,— Leahy said.

Senate Minority Leader Mitch McConnell (R-Ky.) asked Obama not to impose a litmus test on his nominee or use political calculations in tapping a candidate.

“I trust the president will choose a nominee for the upcoming vacancy based on their experience and even-handed reading of the law and not their partisan leanings or ability to pass litmus tests. A Supreme Court nominee needs to be able to fulfill the judicial oath of applying the law without prejudice, and not decide cases based on their feelings or personal politics,— McConnell said.

Sen. Arlen Specter (Pa.), who as chairman of the Judiciary Committee shepherded the nominations of Chief Justice John Roberts and Justice Samuel Alito, also praised Souter and said Friday that he would like to see Obama nominate a woman and/or someone who represents a racial minority.

“I think another female justice would be a good idea. I think given the proportion of women in our society, one out of nine is underrepresented. But the court could use some diversity along a number of lines,— Specter said, explaining that he would also like to see black or Latino candidates for the court.

Noting that he has in the past backed conservative- and liberal-minded judges, Specter said he would not place an ideological litmus test on the nominee, but rather would evaluate them on their qualifications.

“I have never placed a litmus test on Supreme Court nominees. I have supported nominees who are very conservative like Justice [Antonin] Scalia, I’ve supported nominees like Ruth Bader Ginsburg who are very liberal,— Specter said, adding that “I’m looking for a nominee with an excellent education background, qualifications, good experience, breadth of knowledge, an open mind and the determination to follow the Constitution and to follow the statutes enacted by Congress.—

Souter’s departure will almost certainly set the stage for a major political battle over the nomination in the Senate. Conservatives have already begun marshalling their forces to oppose any nominee whom they view as not being a strict constructionist and have denounced Obama’s desire to nominate someone who can empathize with citizens.

Indeed, Sen. Chris Dodd (D-Conn.), said it is “almost impossible to avoid— controversy over Obama’s nominee in the current political climate.

But Specter said he still hopes the process will not degenerate into a partisan food fight.

“My hope is that we will have dignified hearings, as we did when I presided on the hearing of Chief Justice Roberts, that we will evaluate the nominees with respect to educational and professional background, on their adherence to following the constitution and the statutes enacted by Congress and not making law. And we will cast votes on the merits,— Specter said.