Sens. Trent Lott (R-Miss.) and Ben Nelson (D-Neb.) are racing to round up support for an emerging bipartisan compromise that could avoid a meltdown over judicial filibusters.

The plan would pave the way for votes on four nominees in exchange for Republicans’ withdrawing their threat to eliminate the filibuster on judicial nominations, sources said. Republicans would also agree not to pursue votes on the three remaining nominees being filibustered by Democrats — though it is unclear which nominees would be affected.

“The proposal will force a gut check on both sides,” said a source with knowledge of the proposal, who spoke on condition of anonymity. “Democrats will have to decide whether they want to keep up the fight, and Republicans will have to decide if they can take ‘yes’ for an answer.”

The deal is a short-time fix that would cover only the seven most controversial appellate court nominees. It makes no mention of an expected Supreme Court battle later in the year, sources said.

Susan Irby, Lott’s spokeswoman, said she was unable to speak to the state of any negotiations. David DiMartino, Nelson’s spokesman, said he, too, could not talk about the negotiations.

“It is no secret that Sen. Nelson has been working to find a compromise on the nominations issue, but we are not at liberty to discuss any proposal or private conversations at this time,” DiMartino said.

The proposed compromise comes as Democrats and Republicans are each marshaling their resources to prepare for the high-profile fight, which would affect not only Bush’s nominees, but also the way the Senate conducts business. Republicans claim Democrats are leaving them no choice but to consider changing a longstanding Senate rule.

Minority Whip Dick Durbin (D-Ill.) acknowledged Monday that some talks have been under way, revolving around a fixed number of the controversial appellate court nominees being cleared for confirmation while a few others are held back by Republicans and the White House. “That has been part of the conversation,” Durbin said.

Durbin said his party would not accept a deal that limited its ability to filibuster Supreme Court nominees. “There’s been no suggestion we would accept a partial — a mini-nuclear option,” he said.

Amy Call, a spokeswoman for Majority Leader Bill Frist, said the Tennessee Republican was also aware of the ongoing negotiations, but she added, “We are not going to comment on any details.”

The rule modification — known commonly as the “nuclear” or “constitutional” option — would allow judicial nominees to pass with only 51 votes, instead of the current 60 to end debate on a filibuster. Democrats successfully filibustered 10 of Bush’s nominees in the 108th Congress. Of those 10, seven have been re-nominated for positions on the federal bench.

If Republicans follow through on their threat to change the rule, Democrats have vowed to slow legislative business in the chamber to a snail’s pace.

In anticipation of the battle, Democrats deployed four of their Senate leaders Monday to decry the proposed rules change.

At a breakfast meeting with reporters, Minority Leader Harry Reid (D-Nev.) declared that his party was prepared to engage Republicans should the GOP successfully change the rule.

“If Republicans go ahead and break the rules, Democrats are going to use the rules to fight for relief at the gas pump, stronger schools, lower health care costs and a range of other issues important to the American people,” said Reid, according to a prepared statement released by his office following the breakfast.

Later in the day, Durbin explained how his party would do this. He laid out a plan that would involve any Democratic Senator asking for motions to proceed to bills favored by the minority party, a rarely used tactic to call up a bill that has been placed on the Senate’s legislative calendar.

Democrats have added 13 bills to the calendar in the past few weeks, preparing for the post-filibuster fight by putting legislation on the docket that would be politically favorable to their side.

Durbin said that the motions to proceed to the Democratic bills would likely be rejected, since even before a lengthy debate were held on any of the bills, the GOP could motion to table the bills. But bringing them up would consistently put Republicans on the record about hot-button Democratic issues such as raising the minimum wage, Democrats said.

“Instead of shutting down, we want to open the Senate,” Durbin said.

Republicans, however, would be able to maneuver in a similar fashion, by making motions to proceed to any issues they have already slotted on the legislative calendar. For instance, two prime issues for conservative-base voters have slots high up on the calendar. One, a bill to restrict minors from going across state lines to seek an abortion, is sponsored by Sen. John Ensign (R-Nev.). Another, by Sen. Larry Craig (R-Idaho), would limit gun manufacturers’ liability.

GOP aides have suggested in recent weeks that they too could use the calendar to bring up issues that might force Democrats to vote on bills that are politically sensitive to them — particularly those, such as Nelson, who sit in “red states” and are up for re-election in 2006.

It’s still unclear, however, when and how Democrats would force the Senate into this post-nuclear meltdown. Any legislation impacting national security would move in a “timely fashion,” as Durbin put it Monday, which suggests that Democrats would allow such legislation to move on to the floor in the standard fashion of unanimous-consent agreements. The highway bill has also been included in that list, as has every single one of the 13 appropriations measures.

Asked to specify what sort of legislation Democrats would block from moving in a “timely fashion,” Durbin pointed to the energy bill. He also suggested that other items that are included in “wrap up” at the end of a day — nominations and basic legislation that is approved through unanimous consent — would meet a tougher fate and Democrats might force votes on them.

“They will spend more time at their desk, they will spend more time on the floor,” Durbin predicted of Senators.

But, he added, those nominees to critical posts involving international affairs and national security would likely not be held up by Democrats.

In the meantime, Democrats claimed to be gaining political ground in the 2006 Senate races, with Sen. Charles Schumer (N.Y.) telling reporters on a conference call that the “re-elect” numbers for Republican incumbents were “plunging” due to a series of missteps by the GOP in recent weeks, ranging from efforts to save Terri Schiavo, the brain-damaged Florida woman, to pursuing the nuclear option.

“The Republican majority in the Senate is giving the Democrats a great shot in the arm for 2006,” said Schumer, the chairman of the Democratic Senatorial Campaign Committee.

Sen. Robert Byrd (D-W.Va.) offered his own compromise focusing specifically on how to deal with future Supreme Court nominees, which the octogenarian suggested is the reason Republicans want to change Senate rule.

“The White House does not want a filibuster in the Senate to derail a future choice for the Supreme Court,” Byrd said in a speech at the Center for American Progress, a left-leaning think tank.

Byrd proposed the Senate Judiciary Committee “establish a pool of possible Supreme Court nominees for the president to consider, based on suggestions from federal and state judges, distinguished lawyers, law professors, and others with a similar level of insight.”

The Democratic public relations blitz Monday came less than 24 hours after Frist appeared in a highly publicized taped address broadcast to Christian churches across the country.