Updated 12:30 p.m. | The League of Conservation Voters Action Fund — a well-funded environmental group — on Friday endorsed Massachusetts Democratic Rep. Edward J. Markey in his bid for the Senate as a potential primary rival decided against a bid.
Also, Democratic state Sen. Ben Downing, who had earlier floated his name for a potential Senate run, on Friday announced he would not run for the seat soon to be vacated by Democratic Sen. John Kerry.
"After considering every aspect of a possible campaign, I have determined that I will not be a candidate for the U.S. Senate in the upcoming special election," Downing said in a statement.
Downing's decision was a win for Markey and the Democratic Senatorial Campaign Committee, which, along with Kerry, backs the congressman's bid.
It came the same day as the LCV announced its endorsement of Markey.
“There’s been no greater champion in Congress for the clean energy economy than Ed Markey. He has never stopped fighting for Massachusetts — promoting new technologies and green jobs, standing up to corporate polluters, and putting the health of our families first," Scott Nathan, chairman of the League of Conservation Voters, said in a statement. "Ed Markey is the leader Massachusetts needs in the U.S. Senate."
The LCV and its affiliated political committees, including the action fund, spent almost $14 million during the 2012 election cycle.
Kerry is expected to soon be confirmed as secretary of State, setting up a special election for his seat. Markey was the first to announce a bid for the seat.
Other potential Democratic candidates include Reps. Michael E. Capuano and Stephen F. Lynch as well as Rabbi Jonah Pesner.
Former Sen. Scott P. Brown is seen as Republicans' best hope to win the seat, though he has yet to announce a decision on a run.
Friday's endorsement is not the LCV's first foray into Massachusetts Senate politics. In 2011, the LCV knocked Brown in a potent TV spot backed by $1.9 million.