BOSTON (Reuters) - Massachusetts Governor Deval Patrick on Wednesday named his former chief of staff, William Cowan, to fill the U.S. Senate seat that Democrat John Kerry will vacate this week when he becomes secretary of state.
Cowan said he had no plans to run in the June 25 election to choose a permanent successor to Kerry, setting the stage for an intense five-month race.
U.S. Representative Stephen Lynch, a former ironworker, planned to kick off his run for the seat on Thursday, a source with knowledge of his plans said, mounting the first challenge to a fellow Democratic congressman, Ed Markey.
Markey announced his candidacy in late December, less than a week after President Barack Obama nominated Kerry to his Cabinet, with a raft of high-profile endorsements that observers saw as an effort to bypass a primary challenge and focus on the expected Republican contender, former U.S. Senator Scott Brown.
Cowan, a 43-year-old former civil rights lawyer, said he would closely follow Kerry's legislative plans for his time in the office.
"I'm going down in this temporary period to continue the good work that Senator Kerry and his team has been doing," said Cowan. "Senator Kerry has worked in close partnership with Governor Patrick and so you can expect me to do the same."
Massachusetts law would have allowed Patrick to nominate an interim candidate who wanted the permanent post, but the governor said he preferred to see a competitive primary.
Cowan will become the second black member of the current Senate, a distinction that Patrick, who is Massachusetts' first black governor, said influenced his choice.
"The commonwealth and the country is changing," Patrick said. "To the extent that we can reflect that and encourage little boys and girls of color, or who are poor, or who grew up in marginalized circumstances, to imagine what it might be like to serve the public in these ways, I think that's a great thing."
The appointment of Cowan, a married father of two boys who goes by the nickname "Mo," maintains the Democrats' 53 seats in the Senate. Republicans hold 45 and there are two independents.
The Senate on Tuesday approved Kerry to succeed Hillary Clinton as secretary of state. Democrat Elizabeth Warren, elected in November, now becomes Massachusetts' senior senator.
With Kerry's departure from a seat he has held since 1985, Massachusetts loses much of its seniority in the Senate. Kerry served for almost a quarter century before the death of Edward M. Kennedy in 2009 made him Massachusetts' senior senator. Kennedy had held his seat for 47 years.
Cowan, who joined the Patrick administration in 2009, left late last year to return to the private sector.
While he kept a low profile, one former lawmaker said Cowan stood out for a calm but persuasive demeanor.
"We had people in our office yelling, screaming, demanding what would be in a bill or out of a bill ... Mo argued on the merits and was not confrontational," said Steven Baddour, a Democrat who served in the state senate from 2002 through 2012.
Lynch plans to announce his candidacy on Thursday, said the source, who declined to be identified.
The congressman, who has represented Boston and the surrounding area since 2001, will begin his day with a series of appearances in the central part of the state, including the second- and third-most-populous cities of Worcester and Springfield, before an afternoon rally at his old union hall.
Lynch, Markey and any other Democratic contenders will face off in an April 30 primary.
On the Republican side, all eyes are on Brown, who has maintained a low profile since losing his re-election bid to Warren.
Brown stunned Massachusetts' liberal establishment in 2010 when he won a special election to fill Kennedy's former seat, becoming the state's first Republican senator in three decades.
After Markey declared his interest in the office, he quickly banked a number of endorsements from prominent Democrats including Kerry, Victoria Kennedy, wife of the late Senator Edward Kennedy, and state Attorney General Martha Coakley, who was defeated by Brown in 2010.
Former U.S. Representative Barney Frank, who had publicly sought the interim Senate post, on Wednesday threw his weight behind Markey.
Editing by Jackie Frank and Doina Chiacu