The death of Sen. Robert Byrd has thrown the future of financial reform legislation into question just days ahead of an expected final passage vote in the Senate.
Byrd, a West Virginia Democrat, died early Monday morning at the age of 92.
Byrd's death presents the Obama Administration with an unexpected last-minute challengeto the passage of its Wall Street overhaul legislation. Negotiators finished work on the measure last week, and final passage with a narrow margin was expected before the Fourth of July holiday.
The vote now is scrambled because a Republican who had supported an earlier version of the measure said over the weekend that he was reconsidering his position.
Freshman Sen. Scott Brown (R-Mass.) said that he had been surprised by a nearly $20 billion fee that was included in the final legislation in order to force the nation's largest banks to pay for the costs of implementing the new legislation. Brown called that a tax, and said its inclusion might cost his vote.
Democrats had already carved out a loophole for Brown in the so-called Volcker Rule that would allow banks to invest as much as 3 percent of their tangible common equity into hedge and private equity funds.
Brown's statements and Byrd's death put intense focus on the two Democrats who had voted against the initial version of the legislation, saying that it was not tough enough on Wall Street.
The two, Sen. Russ Feingold (D-Wisc.) and Maria Cantwell (D-Wash.), could hold the key to the fate of the legislation.
A senior administration official told CNBC Monday morning that the effort to round up votes for the measure was "a moving target" in the wake of Byrd's death, but expressed confidence that the measure would pass.
"We'll get there," the official said.
Earlier Monday, Sheila Bair, the chairman of the Federal Deposit Insurance Corporation, told CNBC that Byrd's death could affect the passage of the bill .
"It does create a new dynamic," said Bair. "It was razor thin to begin with, so it does introduce a new unknown into the process."
Correction: An earlier version of this report incorrectly identified Scott Brown as a Democrat. He is a Republican.