Over a dozen moderate lawmakers met behind the scenes to head off a Senate showdown over judicial filibusters, but ended talks Wednesday evening before a deal was made.

The centrist senators convened in various offices around the Capitol complex — in Sen. John Warner's office at one point, Republican Mike DeWine's office at another — in an effort to reach a compromise.

Democratic Sen. Ken Salazar (search) of Colorado attended at least 13 private meetings over the previous 24 hours with senators trying to reach a deal, a spokesman said.

"It's kind of like exams. If you have a date certain, people tend to react. So in that sense, this has been a good thing," said Sen. Lindsey Graham (search), R-S.C., one of the negotiators.

The senators seen going in and out of those sessions during the day included Republicans Graham, DeWine, Warner, John McCain (search) of Arizona, Susan Collins of Maine, Mike DeWine of Ohio, Lisa Murkowski of Alaska and Democrats Salazar, Ben Nelson (search) of Nebraska, Mary Landrieu of Louisiana, Joseph Lieberman of Connecticut and Mark Pryor of Arkansas.

Congressional aides said late Wednesday the negotiators failed to reach agreement but would resume their talks Thursday. The aides spoke on condition of anonymity because the discussions are being held behind closed doors.

Although a deal didn't come to fruition, lawmakers remained hopeful that one could be reached — and quickly.

"We're certainly not done. You know, we're not there yet and we may never get there, but you know, I think we're getting closer," said DeWine after one of the meetings.

Added Sen. Ben Nelson, D-Neb.: "The goal is to get it done as soon as possible."

Meanwhile, the Senate's party leaders, Republican Bill Frist of Tennessee and Democrat Harry Reid of Nevada, opened formal debate on Texas jurist Priscilla Owen (search) — the nominee that will test the Democrats' ability to continue blocking judges with filibusters.

In the negotiations, one of the deals being worked on would have the Senate confirming Owen, California judge Janice Rogers Brown and former Alabama Attorney General William Pryor (search), with Idaho lawyer William Myers's nomination scuttled. As part of that deal, two Michigan nominees, David McKeague and Richard Griffin, would be confirmed, while a third nominee — Henry Saad — would be jettisoned.

A fourth Michigan judge, Susan Neilson, also would be confirmed. She has not been filibustered by Democrats in the past.

Senators are still negotiating that part of the deal and it is subject to change, aides said.

Under the latest Republican-crafted proposal, both sides would have to operate on "good faith." Republicans would be bound not to ban judicial filibusters only if Democrats forswear judicial filibusters except for extraordinary situations, aides said.

While not participating in the talks, Frist and Reid are closely monitoring the developments. Negotiators are to meet again Thursday, with Democrats expected to respond to the Republican offer.

The Republicans working on that deal are contradicting Frist, R-Tenn., who has insisted that all of the White House's nominees get confirmed.

"Members of both sides of the aisle recognize from time to time that to get something, you have to give something," Nelson told FOX News Wednesday morning.

"We're still working on the language but I'm not sure that means a withdrawal" of any nominees, Nelson continued, adding that any compromise would include not only a process to follow regarding the seven judicial nominations but also with future nominations.

Top Nelson aides had earlier told FOX News that Nelson and five Democrats are willing to allow floor votes on Owen and Brown, but only if Republicans agree to keep the filibuster — albeit sparingly — and abandon some of the president's lesser-known judicial nominees. Brown is a California Supreme Court justice nominated to the Circuit Court of Appeals for the District of Columbia.

Sen. Orrin Hatch, a Republican on the Senate Judiciary Committee, credited Nelson for standing up and working with Republicans on a compromise.

"He's been sort of a voice in the wilderness over on the Democrats' side," Hatch told FOX News.

But Democratic leader Reid of Nevada said his party would fight to retain what power it still had in a Washington run by a Republican president and GOP houses of Congress.

"If Republicans roll back our rights in this chamber, there will be no check on their power," said Reid. "The radical right wing will be free to pursue any agenda they want. And not just on judges. Their power will be unchecked on Supreme Court nominees, the president's nominees in general and legislation like Social Security privatization."

Frist, frustrated by the Democrats' success in blocking Bush nominees, has threatened to call a vote on banning judicial filibusters. If such a move were to succeed, it would give the GOP full control over which nominees could be confirmed for lifetime judgeships since the party controls the White House and has a 55-44-1 majority in the Senate.

The filibuster, a parliamentary stalling device used by legislative minorities, can be overcome only by a majority of 60 votes or more in the 100-member Senate.

If majority Republicans opt to change the rules to disallow filibusters of judicial nominees — a change labeled the "nuclear option" — parliamentary warfare between Democrats and Republicans could escalate and stall Bush's legislative agenda.

A GOP source close to the behind-closed-doors negotiations told FOX News Wednesday that the situation is "incredibly fluid" and the greatest challenge is mapping out language on the nuclear pledge and on which judge Democrats would have to agree to confirm.

Democrats already have prevented final votes on 10 of Bush's first-term appeals court nominees, and have threatened to do the same this year to seven the president has renominated, including Owen and Brown. The Senate has approved 208 Bush judicial nominees, including 35 appeals court judges.

Just a majority of senators present are needed to approve a nominee once a vote is called in the Senate, and only 50 if the vice president, who breaks ties, votes in favor of a nominee.

Frist also could prevail with 50 votes supporting his move to rule filibusters out of order when used to block a confirmation vote because the Republicans have Vice President Dick Cheney to break a tie.

Neither side appears certain it has enough votes to prevail if that issue is put to a test.

FOX News' Liza Porteus and The Associated Press contributed to this report.