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Patrick appoints former chief of staff interim senator; first time there will be two black senators

Updated, 11:08 am ET, Jan. 30: Massachusetts Gov. Deval Patrick (D) appointed his former chief of staff, William "Mo" Cowan, to be the interim U.S. Senator to replace John Kerry. (Kerry was confirmed Tuesday as Secretary of State.)

Cowan will be one of just two African Americans serving in the U.S. Senate -- Republican Tim Scott of South Carolina being the other. But it is the first time the U.S. Senate will have two black senators serving at the same time. Both Cowan and Scott, however, were appointed. The last black senator before that was also appointed -- Roland Burris. The last elected black senator was Barack Obama.

Massachusetts appointed his former chief of staff, William "Mo" Cowan, to be the interim U.S. Senator to replace . NBC's Brian Williams reports.

Cowan will also be Massachusetts' second black senator. The first was Republican Ed Brooke, who served from 1967 to 1978.

This now means that newly elected Sen. Elizabeth Warren (D) becomes the senior senator from Massachusetts. That represents a remarkable shift from the seniority Massachusetts had just a short time ago when both Sens. Ted Kennedy (D) and Kerry served at the same time.

"Mo's service on the front lines in our efforts to manage through the worst economy in 80 years and build a better, stronger Commonwealth for the next generation has earned him the respect and admiration of people throughout government," Patrick said in a statement. "The people of the Commonwealth have benefited from his wisdom and good judgment during his time in our office, and will again in the Senate." 

For his part, Cowan said, "I am honored and humbled by this appointment today. I pledge to you and the people of Massachusetts that during this interim period I will work as hard as humanly possible to perform my duties with the needs and aspirations of our state's citizens foremost in mind."

“I am very pleased to welcome Mo Cowan to the Senate," Warren said in a statement. "As former chief of staff to Governor Patrick, Mo brings a deep knowledge of the issues facing the people of our Commonwealth to the Senate. He will be a committed, hardworking interim Senator, and I look forward to working closely with him to protect the interests of Massachusetts families."

Cowan grew up in humble beginnings in a small town in North Carolina. His mother worked for minimum wage and his father died when he was 16, the Boston Globe reported. Cowan graduated from Duke University and then moved to Boston to attend Northeastern Law School. 

On Wednesday, John Kerry said farewell to his Senate home of 27 years, as he prepares to take on a new role as Secretary of State. NBC's Brian Williams reports.

Cowan stayed in Boston to practice law and became friends with Patrick while both were attorneys.

Cowan also helped former Republican Gov. Mitt Romney, and 2012 Republican presidential nominee, identify more diverse candidates for his judicial picks.

Patrick was also considering businesswoman Carol Fulp, who is African American, and Margaret Marshall, the first woman state Supreme Court chief justice.

Former Congressman Barney Frank openly campaigned for the post, but his lobbying is said to have rankled Patrick. Frank also criticized Chuck Hagel, President Obama's pick for Defense Secretary. Obama and Patrick are good friends, having gone to law school together. They've even shared speech writing.

Frank walked back his criticism of Hagel, but that may have been too late.

The state set the special election date for June 25th; the primary will be April 30th. 

Former Republican Sen. Scott Brown says he's now "leaning strongly" toward a run for the Senate again.

The top Democrat is seen as Congressman Ed Markey, but a poll out this week showed Brown as the favorite, if he runs, as he held sizable lead over Markey and other Democrats.

NBC's Luke Russert contributed to this report.