Still stinging from their inability to mount opposition to the nomination of Attorney General Eric Holder, Senate GOP leaders are urging their Conference to avoid making any early pronouncements — and, more importantly, endorsements — of President Barack Obama’s pending Supreme Court pick.

At the same time, Obama has tapped three Senate Democrats — Claire McCaskill (Mo.), Majority Whip Dick Durbin (Ill.) and Conference Vice Chairman Charles Schumer (N.Y.) — to serve as informal advisers in the effort. The president has asked the trio to help him vet and gauge Senate support for prospective nominees.

Obama, for his part, will sit down today to discuss the nomination with Senate Majority Leader Harry Reid (D-Nev.), Minority Leader Mitch McConnell (R-Ky.), Judiciary Chairman Patrick Leahy (D-Vt.) and ranking member Jeff Sessions (R-Ala.). McConnell and other GOP leaders have asked the Conference to hold their tongues until after the formal confirmation process starts, likely sometime next month.

McConnell, according to a senior leadership aide, has stressed to his colleagues that “it doesn’t make any sense to make any pronouncements in the first 72 hours of a process that could take six months.— Supreme Court Justice David Souter, 69, announced he was resigning the court at the end of this term.

Senate Republican leaders are still fuming over the Conference’s handling of Holder’s nomination for attorney general earlier this year. Leaders had been plotting to ramp up opposition to the nomination but were largely sidelined after several high-profile Senators — including Sen. Orrin Hatch (R-Utah) — endorsed the pick.

While Senate Republicans predict that Obama’s first Supreme Court nominee will ultimately be approved, McConnell does not want to completely abdicate to the administration on the choice. GOP leaders want Members to keep their powder dry at first, giving them time to decide whether to wage a full-scale attack or allow for a smooth confirmation.

“I think it’s good advice,— Judiciary Committee member John Cornyn (R-Texas) said Tuesday.

Cornyn argued that waiting to make a pronouncement about Obama’s high court nominee makes sense since the confirmation process is likely to reveal potential problems with his or her fitness for the high court.

“Often there are things that come out during the nomination process that we didn’t know before [and] that can affect how we see a nominee,— Cornyn said.

Politically speaking, GOP leaders are hoping to avoid early intraparty defections or a public split on the nomination. Plus, they want to use the fight to energize the party base and potentially rebuild some credibility with conservatives, who view judicial nominations as a top priority.

Meanwhile, Obama is working all the channels to ensure a smooth confirmation for his first Supreme Court nominee. The White House has begun working with a small group of Democratic Senators to act as both an informal sounding board on potential nominees and as liaisons to the Senate on the matter.

Although Schumer, Durbin and McCaskill are the primary members of the group, Democrats said other lawmakers are also involved, including Leahy, whose panel will hold hearings on the pick.

Obama has used McCaskill, in particular, as a window into how his pick might be viewed by Democratic centrists and female Senators, one Democratic aide said.

Another Senate Democratic aide said Obama will likely count on McCaskill, Schumer and Durbin to act as the chief defenders of his nominee when the candidate comes under attack. Though Obama is not expected to nominate a left-wing ideologue and has been soliciting input from Senate Republicans as well, this aide said the White House does not want to take chances.

“You never want to be too trusting, because of issues where it would’ve seemed we’d get bipartisan support — like on the [economic] stimulus — we didn’t,— the aide noted. “There are already signs the Republicans are going to use the confirmation process to rally their base.—

Neither Schumer nor McCaskill would answer questions related to the Supreme Court nomination on Tuesday, and Durbin has insisted his role has been minor — despite his close personal relationship with the president.

Speaking generally about a potential court pick, however, Durbin said he could envision a scenario where Obama chooses a candidate that has not previously served as a jurist. “It wouldn’t surprise me if the final choice were not someone who has worked their way through the judicial ranks,— Durbin said.

Durbin noted, however, that Members who have been suggesting names to Obama might be “naïve,— given the considerable thought the White House has put into its own list of potential nominees. And Durbin said whomever Obama selects is likely to be put through the wringer by the president, considering Obama’s extensive background in constitutional law.

“This will be unlike any presidential interview in modern times. [Former President] Bill Clinton was smart enough, but when it gets right to it, Obama could give this nominee a final [exam] on constitutional law,— Durbin said.

Sen. Olympia Snowe (R-Maine) said she told the president personally last week that she would prefer he pick a woman for the post. Snowe also wrote Obama on the issue of selecting a woman in a letter she sent to the White House on Monday with Sen. Barbara Boxer (D-Calif.).

Snowe said a nominee like current Justice Ruth Bader Ginsberg would be preferable because she believes Ginsberg has a “very pragmatic approach and style on the court.—

Snowe added, “I think it is important that you have somebody who understands those real-life applications and how they apply under the law.—

But Snowe said Democrats who assume she will vote for almost any nominee that Obama sends up should think again.

“No one should ever consider me automatic. I don’t know if they consider me automatic, but it goes back to who they select,— the moderate Republican Senator said.

Sen. Dianne Feinstein (D-Calif.) said she would be suggesting Obama look to California for his choice. Still, she acknowledged, “This is an intensely personal decision for the president to make. I think his criteria are going to be the criteria that are going to prevail.—

However, Feinstein did have some advice for the president on how to make his own selection. “I do think he has to be sensitive to the ability to get a nominee confirmed because … the history going back to confirmations of Supreme Court justices is very partisan, and, therefore, I think there is merit in avoiding a partisan fight — getting someone in this first appointment who is solid, who is experienced, who has the judicial temperament, knowledge and skill, who understands how law affects people’s lives.—

But if the administration thinks nominating a woman will guarantee the votes of the chamber’s female Senators, several disagreed: “I’d be delighted for it to be a woman. … But I’m not saying at all that it must be a woman,— Sen. Susan Collins (R-Maine) said.