Senate Majority Leader Bill Frist (search) told Democrats that unless they allow an up or down vote on the seven stalled nominees, he will invoke the so-called "nuclear" or "constitutional" option, by which filibusters on nominees will be banned for good.

"The Senate does not require 60 votes to become a judge, only 51 votes ... We're talking about keeping a supermajority from overriding the will of a constitutional majority that has been that way for 214 years," said Sen. Chuck Grassley, R-Neb., who supports invoking the nuclear option (search).

Visual reminders of the battle appeared throughout the morning — Republicans were shipping in cots in anticipation of the late-night debate to come while Democrats prepared a staging area from which to distribute petitions with signatures of Americans opposed to the nuclear option.

Meanwhile, six Democrats and six Republicans were planning to meet Monday evening before the scheduled showdown. Those working on a compromise say they're trying to figure out a way to protect the minority party and end any abuse of the filibuster.

"We're having difficulty coming up with exact language which would portray that desire. It's tough," Sen. John McCain, R-Ariz., told "FOX News Sunday."

A draft memorandum of understanding from Friday's negotiations said Democrats and Republicans signing the compromise would take several steps designed to avert a showdown "based upon mutual trust and confidence."

For Democrats, that meant agreeing to clear the way for final votes on six contested judges, including conservative Texas Supreme Court Justice Priscilla Owen (search). Two other nominees would not be guaranteed final votes.

In addition, the draft said future nominees to the appeals court and Supreme Court "should only be filibustered under extraordinary circumstances." Each senator would be permitted to decide when that condition had been met.

In return, those agreeing to the compromise would "commit to oppose the rules changes" sought by Frist. For Republicans that would mean breaking ranks on the issue "to reduce the rancor that unfortunately accompanies the advice and consent process in today's Senate," the draft said.

If the deal doesn't shake out, Republican leaders say they believe they have the votes to end the filibuster, but some are concerned about Democrats responding by shutting down the Senate.

In turn, Democrats said it is Republicans who are shutting down essential operations by the Senate by refusing to allow senators to invoke their constitutional "advise and consent" role.

"That contempt for the rule of law, the law of rules, will set a new precedent — an illegal precedent — that will always remain on the pages of Senate history — a precedent that will thrust us toward totally eliminating the filibuster in all Senate proceedings, a precedent that will eliminate the essential deliberative nature of the Senate," Senate Minority Leader Harry Reid (search) of Nevada said during a commencement address at George Washington University's law school.

Frist's timetable calls for the critical votes on Owen to be cast Tuesday and Wednesday.