The death of U.S. Senator Edward Kennedy already is generating speculation on who will succeed him.
A special election must be held in Massachusetts to pick his successor. Most states allow the governor to name a temporary replacement in the event of a vacancy in the U.S. Senate. But that is not the case in Massachusetts, where state law mandates a special election no sooner than 145 days and no later than 160 days after a vacancy occurs.
The law bans an interim appointee.
Many younger Kennedys are active in civic life, but none on the scale of Ted Kennedy. His son, 42-year-old Patrick, is a congressman from neighboring Rhode Island, and is the only Kennedy family member still holding public office. He would need to move to Massachusetts if he were ever to run for his father's seat.
One of Ted Kennedy's nephews, former Congressman Joseph Kennedy, has been mentioned as a possible successor.
Other potential Democratic candidates include the state's governor, attorney general and several Massachusetts members of Congress. There also are several potential Republican candidates for the post.
Massachusetts is dominated by Democrats, perhaps more than any other U.S. state.
In 2004, the Democratic-controlled state legislature passed the law requiring a special election after such a vacancy in the U.S. Senate delegation from Massachusetts.
Democratic leaders pushed for the bill after U.S. Senator John Kerry won the Democratic presidential nomination that year. They feared that then-Republican Governor Mitt Romney would name a Republican to replace Kerry if he defeated then-President George W. Bush.
Just last week, Ted Kennedy wrote a letter to state lawmakers urging them to give Governor Deval Patrick the power to appoint an interim successor in case he was forced to vacate the seat.
Some information for this report was provided by AP and Reuters.