The Senate parliamentarian holds an obscure position in Congress: chief arbiter of the chamber's Byzantine rules. But the man who holds the post could help make or break any health care bill enacted via a budget maneuver called reconciliation.
The legislative two-step, which both parties have used, is designed for funding matters. When it comes to its use, the parliamentarian's job is to decide which provisions directly impact the budget, and which do not and should be stricken from usage.
How the parliamentarian -- Allan Frumin -- will act has become something of a parlor game in Washington, with one reporter suggesting political hacks may try to divine his potential rulings based on clues like his facial hair or his hometown.
Longtime associates say Frumin, who has been in the parliamentarian's office since 1977 and has been chief parliamentarian since 2001, would rule conscientiously.
"He doesn't do it from the point of view of policy. He's made Democratic senators very angry in the past; he's made Republican senators very angry in the past. And he is not a party hack," said Ilona Nickels, author of "Why Congress Matters."
Under the "Byrd rule," named after West Virginia Democratic Sen. Robert Byrd, if the parliamentarian identifies items in a health care reconciliation bill not directly related to the budget -- abortion provisions, for instance -- a lawmaker can motion for those items to be removed, and the parliamentarian's ruling will be sought.
"We know that we have some other senators, for example, from the Budget Committee, that might be very sensitive about establishing precedent that they have to live with in the future, that go against the process that they depend on as a budget tool," Nickels said.
If Frumin's ruling is disputed, the question may proceed to the chamber's highest authority -- the president of the Senate, who happens to be Vice President Biden.
"The vice president has the independent ability as a presiding officer to frame questions for the Senate to decide when it comes to reconciliation as he does on many other matters. He's obviously informed by precedent and past practice but he can put a question to the Senate however he chooses to frame it," said former GOP Senate aide Eric Ueland.
"The parliamentarian only can advise, it is the vice president who rules," former Parliamentarian Robert Dove told MSNBC on Monday. "But I will say that not since Hubert Humphrey have I seen a vice president try to play that kind of role in the Senate."
If Biden overrules Frumin, a senator can appeal, but a Biden supporter could move to quash or "table" the appeal, a matter that would then be decided by a simple majority vote.
"This could potentially disadvantage individuals who are attempting to use the Byrd rule to strike out or modify provisions of a reconciliation proposal when it is before the Senate," Ueland said.
Yet even some champions of the health care overhaul may wince at seeing Frumin's rulings cast aside.
"We don't know that all Democrats are going to be lockstep behind whatever the vice president decides to do with the parliamentarian's ruling," Nickels said.
Fox News' James Rosen contributed to this report.