BOSTON — Gov. Deval Patrick today named Paul G. Kirk Jr., a former aide and longtime confidant of the late Senator Edward M. Kennedy, to Mr. Kennedy’s seat.
“He shares the sense of service that so distinguished Senator Kennedy,” Governor Patrick, a Democrat, said at a news conference in Boston. “The interests of the commonwealth have never been more vital or at stake in the Congress today.”
Mr. Kirk, a longtime friend of the Kennedy family and onetime special assistant to Senator Kennedy, is scheduled to take the oath of office on Friday and serve until a special election on Jan. 19; he has pledged not to run in the election. He said on Thursday that he would keep the late senator’s staff in place.
Mr. Kirk was the favorite of the late senator’s wife and two sons, as well as some officials in President Obama’s administration, according to people familiar with the matter. The president issued a statement after the appointment was announced.
“I am pleased that Massachusetts will have its full representation in the United States Senate in the coming months, as important issues such as health care, financial reform and energy will be debated,” Mr. Obama said. “Paul Kirk is a distinguished leader whose long collaboration with Senator Kennedy makes him an excellent interim choice to carry on his work until the voters make their choice in January.”
On Wednesday, the Massachusetts legislature gave final approval to a bill that allowed Mr. Patrick to name an interim successor to Mr. Kennedy, who died of brain cancer last month.
Late Thursday morning, however, the Massachusetts Republican Party filed a motion in Suffolk Superior Court requesting an injunction to keep the appointment of Mr. Kirk from taking effect. In its motion, party leaders argue that it was unconstitutional for the governor to have put the new law into effect immediately.
“It’s in the judge’s hands now,” said Tarah Donoghue, communications director for the state party.
A person close to the Kennedy family said Wednesday that Mr. Kennedy’s widow, Victoria Reggie Kennedy, and his sons, Edward M. Kennedy Jr. and Representative Patrick J. Kennedy of Rhode Island, had urged Mr. Patrick to appoint Mr. Kirk, who worked for Senator Kennedy in the 1970s, and later served as chairman of the Democratic National Committee.
Mr. Kirk said he was grateful the family chose him “to be a voice and a vote” for the late senator’s causes.
“This appointment is a profound honor, and I accept it with sincere humility,” he said.
The other Massachusetts senator, John Kerry, said at the news conference that Mr. Kirk would be a “superb steward” for Mr. Kennedy’s seat.
Mr. Kirk, 71, is chairman of the John F. Kennedy Library Foundation in Boston. Several friends and associates described him as low-key and laconic, a shrewd political strategist who could have run for office himself but decided he preferred a behind-the-scenes role.
Democrats in Washington and Massachusetts expressed enthusiasm for his candidacy, saying Mr. Kirk was familiar enough with Capitol Hill and Mr. Kennedy’s priorities to seamlessly pick up where the senator left off.
Just before Mr. Kennedy died on Aug. 25, he asked the legislature to change the law and let Mr. Patrick appoint a temporary replacement for his seat until a special election could be held. That election is scheduled for Jan. 19.
Although Mr. Kennedy did not mention it when he made the request, it is clear that Democratic votes will be crucial to passing the contentious health care legislation making its way through Congress. He was a champion of overhauling the health care system, but with his seat empty, Democrats in the Senate are not assured the 60 votes necessary to pass the legislation.
Under the State Constitution, Mr. Patrick has to take the unusual step of declaring the law an emergency to make it effective immediately; most new laws cannot take effect for 90 days.
State Republicans said they might try to block an emergency declaration, and indeed late Wednesday, several House Republicans asked Mr. Patrick to seek an advisory opinion from the state’s Supreme Judicial Court on whether he had the authority to make such a declaration. But William F. Galvin, the secretary of state, said there were no grounds for a legal challenge. “This procedure goes on all the time,” said Mr. Galvin, a Democrat.
Mr. Patrick returned to Boston on Wednesday after several weeks recuperating from hip surgery at his home in western Massachusetts.
In addition to Mr. Kirk, Mr. Patrick was said to have considered Michael S. Dukakis, a former governor and 1988 presidential nominee, and Evelyn Murphy, a former lieutenant governor under Mr. Dukakis.
Republicans, who have fought the succession bill, tried again Wednesday to stall or quash it. Governors here had the power to fill Senate vacancies until 2004, when the Democratic majority in the legislature changed the law to require a special election. Democrats worried then that if Senator John Kerry were elected president, Gov. Mitt Romney, a Republican, would appoint a Republican.
The Constitution states that to put a new law into effect without delay, a governor must write a letter to the secretary of state declaring that “the immediate preservation of the public peace, health, safety or convenience” requires it.
As an alternative, the legislature can declare a new law an emergency, but it requires a two-thirds vote. Both chambers tried but failed Wednesday to muster enough votes for such a declaration.