The longest-serving United States Senator in history won re-election in 2006, at the age of 89, by carrying 54 of his state's 55 counties. Now 90 years old, Robert Byrd is a living legend on the Senate floor, though recent health troubles have led some of his colleagues to question whether he is up to the grueling task of managing another season as chair of one of the most powerful committees in Congress.

Several Senate Democrats, Roll Call reported, spent the week trying to gently nudge Byrd aside as chairman of the Appropriations Committee, concerned about his health and ability to guide complex spending bills through the Senate. Byrd, who returned to the Senate after a recent hospital stay to be greeted warmly by colleagues from both sides of the aisle, spent part of last week making phone calls to fellow Democratic senators hoping to shore up his position as chairman.

Byrd has not managed a bill on the Senate floor in a year, and he hasn't even chaired an Appropriations Committee hearing since September. Last week, Roll Call reported, he canceled a subcommittee hearing on mine safety, an important issue to his home state of West Virginia, a move that caused concern among Democrats.

Over the last week, at least three Senators have been mentioned as potential replacements: Vermont Senator Patrick Leahy privately expressed interest in the position, trying to meet with Senate Majority Leader Harry Reid a few times last week, sources told The Hill. Washington Senator Patty Murray, who has taken to managing more appropriations bills for Byrd in recent years, has been mentioned as a possible successor, as well, as has ranking committee member Daniel Inouye, of Hawaii. Each has vehemently denied the notion that they are interested in the spot as long as Byrd is in Congress.

Some senators have already expressed their public support for Byrd remaining on the high-profile panel. Louisiana Senator Mary Landrieu and Nebraska Senator Ben Nelson, both panel members, have told the press that they support staying on. And while no member will come out and say publicly that they think Byrd should step down, a meeting of Senate Democratic leaders last week did bring up whether he can continue, multiple press outlets reported.

Senate Majority Whip Dick Durbin and Senator Byron Dorgan, said to have brought up the issue at the leadership meeting, both strongly denied involvement to The Politico last week.

Should Byrd leave, even temporarily, tradition would dictate that Inouye would take over the top slot as the second-ranking Democrat on the panel (Inouye told The Post's Paul Kane that he did not expect opposition if Byrd stepped down on his own). Leahy is third in line, and he would have to give up his seat on the Judiciary Committee in order to take over Appropriations. Murray is seventh in seniority on the committee, but her increasing work moving bills through the chamber and her position as the fourth-ranking Democrat in Senate leadership could give her an argument for taking over.

But in the Senate, tradition is a compelling argument, and no one can argue that Byrd is less a part of the institution than any other member. Byrd keeps a copy of the Constitution in his breast pocket, and, when facing a crowded hallway on a recent trip to the Senate floor, told aides, press and fellow senators to "make way for liberty." He has written more extensively on the chamber's history than virtually anyone else, be they senators, academics or historians.

To dislodge such a figure will be difficult for Democrats, and those behind any move will have to tread lightly to achieve success. For his part, Byrd, who knows Senate rules and procedure better than most parliamentarians the body hires, has made it known that he intends to stay, and that, in the world of the Senate, could be the final word.