Niki Tsongas (D), running to replace departing Rep. Marty Meehan (D) in the 5th district, announced Wednesday that the Congressman’s wife will serve as her campaign chairwoman, further underscoring that Tsongas is Meehan’s heir apparent.

In a clear signal that Tsongas has Meehan’s backing, Ellen Murphy Meehan — who runs a consulting firm that services health care providers — has joined her campaign. With a possible crowded primary to replace Meehan in the Democratic-leaning seat, the Congressman’s support could prove key to Tsongas’ prospects.

Meehan, meanwhile, will vacate his Lowell-based seat no later than July 1 to become chancellor of the University of Massachusetts at Lowell, his alma mater. A special election to replace him is scheduled to follow later this year.

Tsongas, a college administrator, is the widow of former Sen. Paul Tsongas (D-Mass.). She is joined in the top tier of candidates interested in succeeding Meehan by Eileen Donoghue (D), the former mayor of Lowell and currently a member of its city council, and Middlesex County Sheriff James DiPaola (D).

Some insiders also believe that David O’Brien, a Democratic National Committeeman, could be a formidable candidate.

— David M. Drucker