Senators Lindsey Graham and Mike DeWine do not believe that the nuclear option is permanently off the table:

DeWine and Sen. Lindsey O. Graham (R-S.C.) have disputed the assertion by Reid and other Democrats that the nuclear option is off the table. DeWine said he explicitly raised the issue just before the group announced the deal on Monday night. "I said at the end, 'Make sure I understand this now, that . . . if any member of this group thinks the judge is filibustered under circumstances that are not extraordinary, that member has the right to vote at any time for the constitutional option.' Everyone in the room understood that."

It may very well be that, in the face of heavy criticism from the Republican base, Senator Dewine may be engaged in some revisionism in order to put the best face on a bad agreement. But Senator Mark Pryor seems to back him up:

Sen. Mark Pryor (D-Ark.), another member of the group, concurred, saying that while he hopes the nuclear option is gone for the duration of the 109th Congress, circumstances could bring it back. "I really think Senator DeWine and Senator Graham have it right," he said.

A statement by Senator Joseph Lieberman throws further confusion in to the issue:

A statement from Sen. Joseph I. Lieberman (D-Conn.) on the future of the nuclear option offered enough ambiguity on whether judicial philosophy constitutes grounds for a filibuster to illustrate why, even within the Gang of 14, the future could be difficult. The statement came in response to a question about whether Reid or DeWine and Graham were properly interpreting the group's deal.

"Our agreement is based on mutual trust and respect among the 14 senators," Lieberman said. "We have the shared intention that the Democratic signers will not filibuster, except in extraordinary circumstances, and that the Republican signers will not invoke the nuclear option. I'm confident that the agreement will be honored and stand the test of time."

The problem, of course, is that the definition of "extraordinary circumstances" to the Democrats is likely going to seem completely unreasonable to Republicans - except maybe for John McCain - when the inevitable filibuster by Democrats arrives. When the Democrats, as they probably will with the arrival of a Supreme Court nominee, set a very low threshold for what they consider "extraordinary," we are likely to see the return of the nuclear option. That will happen without regard to what Robert Byrd, Joseph Lieberman or Harry Reid think they understand the agreement to mean.