Updated: 12:55 p.m.Rep. Mike Capuano (D-Mass.) is adding another name to his recent wave of endorsements for his Senate campaign. Rep. Ed Markey (D), the dean of the Massachusetts House delegation and the latest Member to endorse in the Dec. 8 special Senate primary, will formally announce his backing Tuesday afternoon in an appearance with Capuano in Malden, Mass., the Capuano campaign announced.That brings Capuano’s endorsements from his fellow Massachusetts Congressmen to seven. Rep. Niki Tsongas (D) is the only Bay State Member to endorse someone else. She is backing state Attorney General Martha Coakley (D). Rep Bill Delahunt (D) has not taken sides in the primary.Capuano was endorsed by the Boston Herald on Monday and by former Gov. Michael Dukakis (D) a day earlier.Polls have shown Coakley ahead, but the four-way race appears to be fluid. The primary winner will be heavily favored in the January special election to replace the late Sen. Edward Kennedy (D), who died in August.