Senate Democrats have failed to satisfy both liberals and moderates in their search for a compromise on judicial filibusters, with liberal allies in the House and outside activists angry about the offer and at least one critical GOP moderate outright rejecting it.

With Senate Democrats willing to allow some controversial appellate court nominees to pass and making a generic offer to filibuster less often, the Congressional Black Caucus decided on Wednesday to mount an offensive to stop any compromise.

The CBC will be spending the coming days meeting with Democratic and Republican Senators to encourage them to oppose any changes to the current rules. CBC officials say they opted to weigh in now because a deal could be in the works.

“We are not content to allow it to play itself out,” said CBC Chairman Mel Watt (N.C.). “We need to express ourselves about the important role [the filibuster] plays in the judicial appointment process. It is critical that we protect ourselves.”

Watt will be attending today’s weekly lunch sponsored by the Democratic Policy Committee, specifically to stiffen the Democratic position on the issue. He said Wednesday that CBC members fear that an end to the filibuster could spell disaster for black Americans who more than most rely on a fair and impartial judiciary. The CBC also will convey its concern that the move could adversely affect women’s legal rights, such as abortion and equal pay.

Rep. Elijah Cummings (D-Md.), Watt’s predecessor as head of the CBC, said it is “a very critical moment for the Senate. What they do here will very well affect history.”

One senior Senate Democrat said Minority Leader Harry Reid (D-Nev.) made the offer to Majority Leader Bill Frist (R-Tenn.) in part to send a signal to wavering Republicans that Democrats were offering an olive branch. It could serve as an idea to latch onto, rather than forcing moderates to side with Democratic filibusters or backing the Frist-led nuclear option, which would end filibusters on judicial appointments.

With just a handful of Republicans maintaining that they are undecided on the issue, the senior Democrat said the Caucus wanted to give those GOP Senators another option.

It’s unclear, however, whether the strategy worked. Sen. Susan Collins (R-Maine), who has remained undecided on the issue, rejected the offer by Reid and called it “very strange,” noting that the Democratic filibusters of 10 judicial nominees in the 108th Congress were supposedly done because the minority party believed those nominees were extremists.

“I can’t understand their ‘pick-two approach,’” Collins said.

Reid had offered to allow one of the four most controversial appellate court nominees through — either lawyer William Meyers, U.S. Judge William Pryor, Texas Supreme Court Justice Priscilla Owen or California Judge Janice Rogers Brown.

In addition, Democrats were willing to allow nominees to go through without a filibuster for the 6th U.S. Circuit Court of Appeals, where there has been a decade-long logjam between the parties. But Republicans would also have to jettison their most controversial 6th Circuit nominee, Henry Saad.

In exchange, Democrats have expressed a generic willingness to filibuster less often, only when there is an “extraordinary circumstance.”

Other undecided Republicans held their views on Reid’s offer close to their vest, expressing happiness that the two sides are at least talking. “I’m optimistic these two leaders can solve this,” Sen. John Warner (R-Va.) said.

So far, only two Republicans, Sens. Lincoln Chafee (R.I.) and John McCain (Ariz.), have expressed outright opposition to Frist’s efforts to end filibusters on a simple majority, party-line vote. Sen. Olympia Snowe (R-Maine) has expressed some deep unwillingness to go along, but not outright opposition.

Reid needs to coax Snowe and at least three more GOPers to join Chafee and McCain to overturn what would likely be a ruling from the chair that filibustering was no longer permitted.

But this week’s offer has not left a good taste with the CBC and other liberal allies of Senate Democrats — particularly the possible promise to Republicans that their nominees would be filibustered less often.

“It is one of our few safeguards left to guarantee an independent federal judiciary,” Cummings said. “I believe that all members of the CBC expect the Democratic Senators and those Republicans who care about the rights of all citizens to hold fast in maintaining the filibuster.”

Watt acknowledged that the rule has made it more difficult at times for black Americans to pass critical pieces of legislation, including the Civil Rights Act of 1964. But to abandon it, he said, would “be a slap in the face” to minorities.

In the meantime, the five most influential groups on the left that are involved in the judicial nomination fight — People For the American Way, the Leadership Conference on Civil Rights, NARAL Pro-Choice America, the Sierra Club and the Alliance for Justice — issued a defiant statement of the organizations’ principles against the GOP nominees already facing filibusters. While the groups commended Reid for seeking a compromise, their statement reaffirmed their support of filibustering judges.

“We will not endorse any compromise which undermines the principles we have articulated,” the statement said.