It's unclear whether there will be a special election to fill the remainder of the late Sen. Robert Byrd's (D-W.Va.) term.
West Virginia Gov. Joe Manchin III (D) has the authority to appoint Byrd's interim replacement and decide whether to call for a special election.
If a vacancy is declared more than 30 months before the expiration of a senator's term, the appointee serves until a special election is held, according to the state's election code.
Byrd passed away early Monday. His ninth term was to end Jan. 3, 2013.
If Manchin declares Byrd's seat vacant before July 3, according to the state code, there would have to be a special election, likely set for November.
Declaring the seat vacant after July 3 would mean the interim senator would serve until January 2013.
A spokesman for the West Virginia secretary of state's office said they are consulting with Manchin's office to determine how to proceed.
Manchin told the Associated Press Monday that he has no timetable for appointing a successor to Sen. Byrd. Manchin also said he has no intention of appointing himself to the seat.
"Like all West Virginians, the news broke our hearts. Sen. Byrd was a fearless fighter for the constitution, his beloved state and its great people," the governor said in a statement Monday on Byrd's passing.
Secretary of State Natalie Tennant (D) issued a similar statement.
"We will never replace Senator Byrd," Tennant said in a statement. "He truly was a great West Virginian, and the people of our state have lost a trusted and powerful friend in Washington."
The Senate campaign committees are unsure what will happen next.
A spokesman for the Democratic Senatorial Campaign Committee called the process "murky."
Officials with the National Republican Senatorial Committee said Sunday they didn't expect a special election for the remainder of the term.
— Updated at 10:45 a.m.