Markey, who has been a U.S. Representative since 1976, doesn't represent any North Shore towns or cities. The 7th District runs from Winthrop and Revere roughly westward and a bit south toward Framingham.
Markey, the dean of the state's congressional delegation, issued a statement Thursday saying he's decided to run for Kerry's seat.
The Malden Democrat, reported the Boston Herald, said the events of recent weeks, from the devastation of Hurricane Sandy and the tragedy at Sandy Hook Elementary to the fiscal cliff debate, have made it clear Massachusetts needs a senator with what he called the "right priorities and values."
The announcement comes after two potential Democratic candidates said they wouldn't run: Connecticut resident Edward Kennedy Jr., the son of former Senator Edward Kennedy, and Cambridge actor Ben Affleck.
On the Republican side, it is widely expected for outgoing Senator Scott Brown to meet whomever emerges from the Democratic fray.