BOSTON -- A Democratic push to appoint a successor to the late Sen. Edward Kennedy is sparking a political tempest in Massachusetts, infuriating Republicans and dividing Democrats who only five years ago passed a law requiring that voters decide on Senate vacancies.

On a day when members of both parties paid their respects to Mr. Kennedy, a Democratic icon who died this week of brain cancer, Republicans accused Democrats of hypocrisy. In 2004, the state's Democrat-controlled legislature changed the law to prevent the governor from appointing an interim successor after a U.S. Senate seat becomes vacant. Instead, the new law requires that a special election be held between 145 and 165 days after the position becomes vacant.

At the time, Democratic Sen. John Kerry was running for president and Massachusetts had a Republican governor, Mitt Romney. Proponents of changing the law argued that a gubernatorial appointment was undemocratic and that only voters should decide on a replacement. Democrats also feared Mr. Romney would appoint a Republican.

Now, with Mr. Kennedy dying three years before his term was up, some Massachusetts Democrats are reversing course, calling for Democratic Gov. Deval Patrick to appoint an interim replacement to hold office until the special election can be held. They now argue the state shouldn't be without full Senate representation for months, especially with pressing issues such as health care before Congress.

The Massachusetts situation is the latest to erupt over filling vacant U.S. Senate seats, following particularly messy appointments in New York and Illinois.