State Rep. Carl Sciortino (D) announced on Friday on his Facebook page his intent to run to replace Markey in 2014.

“I am running to continue the strong progressive leadership that the families of the Fifth District have always counted on,” he wrote. “I look forward to bringing my record of accomplishment to Washington to fight for our progressive values.”

Sciortino is one of Massachusetts' few openly gay state legislators, and has served in the statehouse since 2005. He is campaigning for Markey, posting frequently over the weekend on his Facebook about his efforts to collect signatures for the lawmaker, a favor Markey would likely return if he ultimately wins the senate seat.

But that's not yet assured, as Markey faces a primary challenge from Rep. Stephen Lynch (D-Mass.). Whoever wins the Democratic primary is likely to go on an take Kerry's seat, as Republicans have not fronted a credible challenger for the race, and while Markey is favored to win, Lynch is expected to put up a tough fight.