Senate Republicans and conservative organizations got to work Friday on their battle plan for President Barack Obama’s first nominee to the Supreme Court — compiling dossiers on likely candidates, developing strategies for the vetting process and powering up their network of grass-roots activists.

Even before Justice David Souter’s surprise decision to retire from the high court was formally announced, conservatives on and off Capitol Hill were hard at work preparing for a bruising nomination fight between a popular president and a minority party looking for a unifying issue.

In announcing Souter’s retirement Friday, Obama laid out a set of criteria that he will use to choose his nominee, placing particular emphasis on the nominee’s need to be able to “empathize— with citizens.

“I will seek somebody with a sharp and independent mind and a record of excellence and integrity. I will seek someone who understands that justice isn’t about some abstract legal theory or footnote in a case book. It is also about how our laws affect the daily realities of people’s lives — whether they can make a living and care for their families; whether they feel safe in their homes and welcome in their own nation,— Obama said.

Senate GOP leaders tread carefully in issuing their initial responses to Souter’s decision and the idea of a forthcoming Supreme Court selection. Yet in nearly every statement, Republican leaders sent the message that they expected Obama to steer clear of a liberal-leaning jurist.

Sen. John Cornyn (Texas), National Republican Senatorial Committee chairman and a Judiciary Committee member, said: “In his replacement, it is my hope that President Obama will select someone who decides cases based on the law, rather than their own personal politics, feelings and preferences. For it is the law, and not his or her heart or political ideology, that should guide a judge’s decision-making process.—

Behind the scenes, however, GOP leaders were hard at work preparing for what they see as an inevitable fight. Republicans said Friday that leadership staff was already assembling a core group of aides on the Judiciary Committee to put together a process to vet Obama’s nominee and communicate the Republicans’ concerns.

Staff is “already engaged with leadership and at their work stations, to say the least,— one senior GOP aide said.

Although the recent defection to the Democratic Party by Sen. Arlen Specter (Pa.) — who was the ranking member on Judiciary — has shifted much of the initial planning onto leadership, this aide said the situation is not as dire as it might have been.

According to key Republicans, as part of the deal that Specter cut with GOP leaders in 2004 to get the Judiciary chairmanship, a number conservative-minded attorneys and staffers were brought on board to help vet, and ultimately move, former President George W. Bush’s judicial nominees. Much of that staff has stayed on board, Republicans said, providing Minority Leader Mitch McConnell (R-Ky.) — and potentially Specter’s replacement in the ranking member job — with significant support.

“It’s not the ideal week for it, but in some ways, it turns out to be a net plus,— the GOP aide said, adding that Specter’s office “tried to put together a conservative group of staff whose expertise in a lot of ways was to confirm conservative judges.—

Although the details of the GOP’s strategy on the Supreme Court vacancy are far from fully developed, Republicans said McConnell will likely shoulder much of the messaging duties, along with Sen. Orrin Hatch (Utah), Minority Whip Jon Kyl (Ariz.) and Cornyn, all of whom are on Judiciary. Republicans also expect Sen. Jeff Sessions (Ala.) — a former judge and a potential replacement for Specter as the top Republican on the Judiciary panel — to also play a key role in formulating and executing the GOP’s strategy.

Republicans are also planning to coordinate closely with outside activist groups like the Judicial Confirmation Network.

Wendy Long, counsel to the conservative group, said dozens of activists from across the country took part in an early morning conference call Friday to map out a plan. Noting that judicial nominations have long been a top priority for conservatives, she said activists were planning to coordinate on “batting down some of his most extreme candidates— before the president makes his selection.

Indeed, by late Friday, conservatives were beginning to circulate brief dossiers about a handful of individuals rumored to be on Obama’s list, including Solicitor General Elena Kagan; Sonia Sotomayor, a judge on the 2nd Circuit Court of Appeals; and Diane Wood, a judge on the 7th Circuit Court of Appeals.

The brief sketches lay out areas of controversy or issues on which the conservatives could argue that the candidates are unfit for the Supreme Court. For instance, the dossier for Kagan takes aim at her lack of experience as a judge, arguing, “It is difficult to see how her experience fundraising for Harvard Law School qualifies her for a seat on the Nation’s high court.—

Long also said the network of organizations will look to hold Senators’ feet to the fire on any nominee who they believe doesn’t meet their standards. “This is going to be one that separates the men from the boys, the wheat from the chaff,— Long said, noting that activists will use votes on Obama’s Supreme Court pick as a litmus test for whether to support Senators facing re-election.

Long argued the upcoming nomination fight could end up a major boon for Republicans, who have lost significant ground in the House and Senate over the last four years. She said the battle “could be a basis for a Republican renaissance— if the GOP sticks to its conservative guns and throws its full energy into opposing Obama’s nominees. “If there’s any issue that can get dispirited Republicans ginned up … it’s a Supreme Court fight.—

Makan Delrahim, a Republican who formerly worked as a Judiciary Committee aide, agreed that the confirmation process will be “politically charged— given the importance of the Supreme Court. The nine-member court currently tilts conservative, and Republicans view it as their only line of defense against a Democratic White House and Congress.

But Delrahim also suggested that— even though the partisans are licking their chops — not all Senate Democrats are necessarily going to support Obama’s Supreme Court selection. For instance, Specter has been an outspoken champion for conservative judicial nominees. The Democratic Conference’s other moderates also will play a key role in determining how smoothly the confirmation process goes.

“Which way does Specter go?— asked Delrahim, who worked on the Judiciary Committee under then-Chairman Hatch. “If he’s going to be running in a primary and expecting Obama’s support, is he going to be much more forgiving? Probably.—

David Drucker contributed to this report.