The Senate shifted into high gear over the weekend as lawmakers and their staffs began intense preparations for the first Supreme Court nomination battle in 11 years, a fight that could reshape the court and at the same time redefine the chamber’s parliamentary rules.

Even without a nominee at hand, both sides engaged in an early skirmish over when hearings would be held by the Judiciary Committee, with some GOP aides floating the idea of a possible three-week interval between a nomination and the beginning of the hearing process.

Judiciary Chairman Arlen Specter (R-Pa.), who has previously suggested hearings would not be held until the traditional time frame of after Labor Day, left open the possibility of hearings during the August recess, as did Senate Majority Leader Bill Frist (R-Tenn.).

“Until we get the nominee, the specifics, I would not rule anything out,” Frist said Friday.

The committee, more likely, would need close to six weeks or more to complete all the requisite background checks as well as waiting for the FBI to conduct its own extensive probe and the American Bar Association to complete its review of the candidate and make a recommendation.

That would put the earliest potential hearings in mid-August. Only once in the past 33 years has there been an August Supreme Court hearing, the one-day Aug. 5, 1986, hearing for Justice Antonin Scalia.

Specter said he wouldn’t “prejudge” hearings in August. “I’m available,” he said.

The immediate goal is setting up an “orderly process” that gets a nominee confirmed before the start of the Supreme Court’s new term, slated for Oct. 3, Frist said.

Democrats immediately demanded that President Bush engage in what they call “meaningful consultation” on the selection, calling for a pick who is similar in ideology to the departing centrist Justice Sandra Day O’Connor, who was confirmed on a 99-0 vote in September 1981.

“This president ought to use the Reagan standard,” Sen. Chris Dodd (D-Conn.) said.

While there was immediate focus on how the deal averting the showdown on judicial filibusters by the “Gang of 14” would hold up, behind the scenes aides and Senators were making preparations for the confirmation process:

• Hearings will be held in the historic Russell Caucus Room, something one senior aide described as a victory of tradition over the television age. That room has hosted some of the Senate’s most historic and contentious hearings, including the 1991 confirmation battle of Justice Clarence Thomas, but it is not as well prepared to handle the modern technologies of 24-7 coverage — television producers, for example, have always preferred the Hart Senate Office Building’s Room 216 over the Russell Caucus Room.

• The Judiciary Committee will be hiring additional staff specifically to handle the added workload the confirmation process brings with it, dipping into a special reserve fund the chamber sets aside each Congress for unforeseen investigations and other issues.

• In a sign of how new the process is to them — 56 of the 100 Senators have never gone through a Supreme Court confirmation — all 55 Senate Republicans were invited to take part in a conference call Friday afternoon to brief them on how the process will unfold.

• The 14 Senators who crafted the deal avoiding the “nuclear” option confrontation will be meeting early the week of July 11 in a previously scheduled get-together in Sen. Ben Nelson’s (D-Neb.) office, which is now expected to be dominated by talk about whether their deal will hold up under the intense spotlight that comes with a Supreme Court nomination.

Groups on the left and right instantly began appealing to their bases with a wave of press releases, e-mail alerts and e-advertisements.

First out of the blocks in terms of ads was Progress for America, the 527 group closely allied with the White House and Senate leadership that has pledged $18 million for a fight in support of Bush’s nominee to the court. The group sent out a comical Web ad to 8.7 million conservatives poking fun at Democrats’ tendency to oppose almost all of Bush’s nominees, suggesting that they’d attack George Washington if he were the nominee for his weak environmental record, which included his decision to chop down a cherry tree.

The liberal coalition that has led the fight against Bush’s nominees quickly held a press conference in the Mansfield Room demanding a “consensus” nominee in O’Connor’s mold.

But conservatives are already pushing for a nominee who upholds a “strict constructionist” view of the Constitution, which would make that individual more likely to oppose the landmark Roe v. Wade decision and many other rulings hailed by liberals. That O’Connor was often the key swing vote on these decisions should not be taken into consideration in selecting the nominee, they said.

“Regardless of the slot, this should be a person that stands by the integrity of the Constitution,” said Sen. Sam Brownback (R-Kansas), a Judiciary member and a leading social conservative in the chamber.

Many legal and political observers had speculated that Chief Justice William Rehnquist’s retirement would the easier nomination to handle, allowing Bush to pick a solid conservative in exchange for the reliably conservative chief justice without changing the balance of the court.

But Sen. John McCain (Ariz.), who led the Republicans in the Gang of 14 negotiations, said Friday that he didn’t think the potential for a filibuster was any greater because the retirement came from O’Connor rather than Rehnquist.

“We’re more likely today to avoid the nuclear option than we were the day” of the deal, McCain said.

The deal has played out according to plan, so far, with six previously filibustered appellate court nominees winning confirmation and two remaining on the sidelines. A fight over O’Connor’s seat is definitely the biggest test yet to the terms of the deal, raising the possibility of a filibuster that some of the seven Democratic signatories might support.

Such a decision by Democrats would likely again trigger the nuclear showdown and prompt Frist to push for the parliamentary move to end judicial filibusters on a party-line vote.

But McCain said his understanding of the agreement, which allowed for a judicial filibuster only under “extraordinary circumstances,” made for no allowances among the dealmakers to opt out and support a filibuster based on whom the nominee was replacing.

“That criteria [only] had to do with the qualifications of the nominee,” he said.

Sen. John Warner (R-Va.), another critical party to the deal, agreed that the retirement of O’Connor rather than Rehnquist makes a filibuster no more likely.

“I think that should not be a criteria,” he said.

But Warner sent what could be considered a political shot across the White House’s bow, hastily calling a press conference to urge Bush to pick a consensus choice who could appeal to a broad majority of Americans at a time when the nation is sharply divided on the war in Iraq.

“This gives him the opportunity to be a uniter, not a divider,” Warner said.

Sen. Edward Kennedy (D-Mass.), who has seen 18 justices take seats on the court in his 43 years in the chamber, called for a “mainstream conservative” to be picked to avoid a contentious battle and suggested that Bush do more than just call ahead of time to inform Minority Leader Harry Reid (D-Nev.) of who the selection will be.

“People know it when they are being consulted, and people know it when they are being told,” Kennedy said.

Senate Democratic leaders had been preparing for a Rehnquist retirement to be announced over the July Fourth recess, and had armed their colleagues with talking points and an explanation of how a Supreme Court confirmation would unfold. But they quickly recalibrated that plan when O’Connor stepped down on Friday.

While pledging to work with Bush, Democratic leaders are instructing their colleagues to emphasize they will not “rubber stamp” his nominee and signaled that there still could be a filibuster.

“We hope this process can be one of consensus, rather than confrontation but that will be up to President Bush,” reads one of the Democratic talking points. “If the President selects someone from outside the mainstream, we will do our duty to maintain our system of checks and balances.”

Mark Preston contributed to this report.