The first reaction many Massachusetts residents had upon hearing Gov. Deval Patrick had named Mo Cowan interim senator was, "Mo who?" Mo Cowan is not a household name. But he's worked behind-the-scenes in the State House since 2009.

"Mo Cowan has been a trusted advisor, friend and professional colleague,” said Gov. Deval Patrick. "He's served this staff as both chief of staff and chief legal counsel."

Patrick said Cowan's role in helping turn around the Massachusetts economy in recent years "has earned him the respect and admiration of people throughout government." He said the state will benefit from the 43-year-old's good judgment.

Cowan will be the eighth African American to serve in the Senate, and his appointment marks the first time two African Americans have served in the Senate at the same time. But Cowan told reporters he will likely return to the private sector immediately after the special Senate election in June.

"This is going to be a very short political career,” Cowan said. “I am not running for office, I am not a candidate for political office, today or any time in the future."

Cowan lives in Stoughton with his wife and two young sons. He said his political beliefs are in line with Democrats Deval Patrick and John Kerry.