Hours after Sen. Edward Kennedy's (D-Mass.) passing from brain cancer at the age of 77, questions abound over who will succeed him, and how long that succession will take.

Massachusetts state law mandates that a special election be held to fill the vacant seat within 145 to 160 days of when the seat becomes vacant, placing the date of a potential special election between January 18, 2010 and February 2, 2010.

But with landmark healthcare legislation -- the trademark political issue of the late senator's lifetime -- in the balance in the Senate, Kennedy wrote Massachusetts lawmakers in recent weeks, urging them to reverse a 2004 law stripping the governor of the ability to appoint a nominee to succeed him quickly in the case of a vacancy.

"I therefore am writing to urge you to work together to amend the law through the normal legislative process to provide for a temporary gubernatorial appointment until the special election occurs," Kennedy wrote to Massachusetts lawmakers and top political officials in the state. Kennedy wanted the governor to be able to appoint a nominee, with the condition that any successor would give a personal commitment to not seek reelection in the following cycle.

The 2004 law was put in place by Democratic lawmakers in the statehouse in order to block then-Gov. Mitt Romney (R) from appointing a Republican successor to Sen. John KerryJohn Forbes KerryEx-Obama official Marie Harf, Guy Benson to co-host Fox News Radio show Five things to know about Russian oligarch Oleg Deripaska Leaders shirking their nations' democratic facades more brazenly MORE (D-Mass.), should Kerry have won the presidential election that year.

It's unclear whether or not state lawmakers could change the law after Kennedy's passing to allow Gov. Deval Patrick (D), a relatively unpopular incumbent, from appointing a senator.

Due to the long incumbencies of Kennedy and Kerry, the state of Massachusetts has not gone through a special election to fill a Senate vacancy since Kennedy himself was elected. Kennedy was elected in a November 1962 special election in a race to fill the vacancy left by his brother, President John F. Kennedy, who was elected president.

The current vacancy weighs on the prospects for healthcare legislation and a number of other legislative priorities for Democrats in the upper house. But some whip counts have long counted Kennedy -- along with another ailing Senate veteran, Robert Byrd (D-W.Va.) -- as unable to vote, leaving congressional Democrats short of the 60 votes needed to break a filibuster, but prepared for the prospect of lawmaking in Kennedy's absence.