Massachusetts is getting another senator with Am Law 200 ties.

William “Mo” Cowan, who became a senior adviser to Massachusetts Governor Deval Patrick in 2009 after spending 12 years as a litigation partner at Mintz, Levin, Cohn, Ferris, Glovsky and Popeo in Boston, has been tapped by Patrick to replace newly minted U.S. Secretary of State John Kerry until a special election is held in June.

Patrick, a former partner at a predecessor firm of Day Pitney who is married to Ropes & Gray labor and employment partner Diane Patrick, chose Cowan to replace Kerry, whose former Senate colleagues wasted little time this week in confirming his nomination as the country’s top diplomat.

Cowan’s appointment to the vacant Senate seat comes a little more than three years after Patrick sifted through several high-profile legal resumes and chose retired Sullivan & Worcester partner Paul Kirk Jr. to replace the late Ted Kennedy as an interim senator representing the Bay State.

Kirk, a former Democratic National Committee chairman, had close ties to Kennedy and took on the interim senator role without plans to contest the seat in the special election that was held in January 2010. Scott Brown upset Massachusetts Attorney General Martha Coakley in that election, only to lose the seat in November to former Harvard Law School professor Elizabeth Warren.

Brown reportedly intends to run again in the upcoming special election, a race that Cowan apparently has no interest in joining. In public remarks Wednesday, Patrick said that he chose Cowan because he wanted someone who could focus on being a senator without being preoccupied by an election campaign. Cowan’s appointment, which will grant him special access perks like a lifetime pass to the Senate floor and a coveted parking spot, has won accolades from his former firm.

“Mo has the experience, intellect, disposition, judgment, and vision to be the consummate interim [U.S. senator],” Mintz Levin chairman R. Robert Popeo said in a statement. “He is intimately familiar with the needs of Massachusetts and its citizens. Those needs and the country’s well-being will be his highest priority.”

“Mo’s service to the governor and his many years in private practice have earned him the respect of virtually everyone with whom he has had contact,” added Popeo. “Our heartfelt congratulations go to Mo and his family, and we wish him every success in this undertaking and in his future endeavors.”

Cowan’s appointment will mark the first time that the Senate has two African American members serving at the same time. Cowan himself left Mintz Levin in November 2009 to become chief legal counsel to Patrick in the governor’s office, where he oversaw the executive branch’s legal operations, as well as judicial nominations. In January 2011, Patrick named Cowan to be his chief of staff, a position that the former Mintz Levin partner said in November he would relinquish this month.

Lawyers from Mintz Levin have long enjoyed close ties to public service in Massachusetts. Last year a former senior partner at the firm, Paul Wilson, was confirmed as a superior court judge with the backing of Cowan and Patrick. (Lawyers and lobbyists have been the second-largest contributor to Patrick’s gubernatorial campaigns, according to nonprofit Project Vote Smart.)

In October, Mintz Levin’s government consulting unit ML Strategies hired away McDermott Will & Emery partner William Weld, who served as governor of Massachusetts from 1991 to 1997.