Unlike most states, a successor to fill Senator Edward M Kennedy's seat in the Senate will be chosen through a special election, not by the governor.
Massachusetts law requires a special election for the seat no sooner than 145 days and no later than 160 days after a vacancy occurs. The law bans an interim appointee.
The law was changed in 2004, when Sen John Kerry, a Democrat, became his party's presidential nominee and Republican Mitt Romney was the state's governor. Before the change, the governor would have appointed a replacement to serve until the next general election. That would have created the opportunity for Romney to install a fellow Republican in office, a move that Democrats who control the state legislature sought to prevent.
Last week, Kennedy asked Massachusetts lawmakers to change state law to give Massachusetts' current governor, Deval Patrick, a fellow supporter of President Barack Obama, the ability to appoint an interim replacement to Kennedy's seat should Kennedy be unable to continue serving.
"It is vital for this Commonwealth to have two voices speaking for the needs of its citizens and two votes in the Senate during the approximately five months between a vacancy and an election," Kennedy said in a letter to Patrick.
Though Massachusetts is dominated by Democrats, a change in the law isn't a sure thing. Patrick, Senate President Therese Murray and House Speaker Robert DeLeo, all Democrats, gave no indication if they would support the change.
Any change could not happen immediately. Lawmakers are not expected to return to formal sessions until after Labor Day. Despite speculation that Kennedy's wife, Vicki, could assume his Senate seat, family aides have said she is not interested in replacing her husband either temporarily or permanently. One of Kennedy's nephews, former Rep Joseph P Kennedy II, has also been described as interested.
Any race to succeed Kennedy would be crowded and fiercely fought. Other potential Democratic candidates include state Attorney General Martha Coakley, US Reps Stephen Lynch, Michael Capuano, Edward Markey, James McGovern and William Delahunt, and former Rep Martin Meehan, now chancellor of the University of Massachusetts at Lowell.
On the Republican side, potential candidates include Cape Cod businessman Jeff Beatty, former Lt Gov Kerry Healey, former US Attorney Michael Sullivan and Chris Egan, former US ambassador to the Organization for Cooperation and Development.