1/30 Update: Gov. Deval Patrick has named his former chief of staff, William “Mo” Cowan, to the interim Senate post.
BOSTON — Gov. Deval Patrick is keeping his choice for interim U.S. senator close to the vest.
Patrick is promising to announce on Wednesday his choice to temporarily fill Sen. John Kerry's seat until a special election is held in Massachusetts on June 25. Kerry was confirmed by the Senate on Tuesday to be the nation's next secretary of state.
Former U.S. Rep. Barney Frank is the only person who has publicly expressed interest in serving as the interim senator.
Other names that have drawn speculation include Carol Fulp, a Boston business and civic leader; William "Mo" Cowan, the governor's former chief-of-staff; Victoria Kennedy, widow of the late Democratic Sen. Edward Kennedy; and former Democratic Gov. Michael Dukakis.
Patrick has said his selection will be a person who is not planning to run in the special election and someone who will be "a good steward" for the commonwealth until voters have their say during the special election.
The race to replace Kerry is slowly beginning to shape up.
The only announced candidate is U.S. Rep. Edward Markey, the longest serving member of the state's all-Democratic congressional delegation.
Markey has already won the backing of Victoria Kennedy and the chair of the Democratic Senatorial Campaign Committee. Kerry has also signaled his support for Markey, stopping short of an outright endorsement.
Markey had hoped to clear the Democratic field to avoid a primary, but fellow Democratic Congressman Stephen Lynch is preparing to make a major announcement Thursday and is widely expected to say he is a candidate for the seat.
Lynch will begin a tour of Massachusetts on Thursday morning with stops in Springfield and Worcester and an evening event at Iron Workers Local 7 in South Boston.
The Boston Democrat has been privately telling supporters of his plans to run, although he publicly said last week that he had not made a final decision.
The biggest question mark is former U.S. Sen. Scott Brown who hasn't said whether he will be a candidate on the Republican side.
Brown won the 2010 special election for Kennedy's seat following Kennedy's death, but lost a bruising re-election battle last year to Democratic Sen. Elizabeth Warren. He remains popular among voters and still has a statewide political organization.
Brown has demonstrated an ability to raise tens of millions in campaign donations and would be considered a front runner, although he would still encounter the hurdles any Republican faces in Massachusetts, which typically favors Democrats.
Brown has given no indication yet whether he's planning to run.
The primary is set for April 30.
Timing is tight. Candidates will have just four weeks to collect the 10,000 signatures needed to get on the ballot. There's also little time to do the fundraising and statewide campaigning needed to secure a victory.
Whoever wins will face a re-election campaign in 2014.
Markey publicly challenged all Democratic and Republican candidates who might jump into the special election to agree to keep outside groups from spending money on political ads - similar to the so-called "people's pledge" in last year's Senate race, which was also the most expensive political contest in state history.
Kerry has represented Massachusetts in the Senate for nearly three decades. His departure brought praise from top elected officials Tuesday. Patrick called Kerry "our steadfast champion" for Massachusetts.
"We are sad to lose him as our senator, but excited about and grateful for his service to the nation on the international stage," Patrick said.
Warren, who becomes the state's senior senator after less than a month in office, called Kerry "a true statesman" whose life experience "uniquely qualifies him to represent the people of the United States around the world."
In his resignation letter, Kerry talks about his "great gratitude to the people of Massachusetts for the privilege of serving them for 28 years."
His resignation takes effect at 4 p.m. Friday.
This article was originally published on January 29, 2013.
This program aired on January 29, 2013. The audio for this program is not available.