CBS Boston is reporting that Massachusetts Governor Deval Patrick will appoint William "Mo" Cowan to temporarily fill Senator John Kerry's seat once Kerry is sworn in as Secretary of State today:

(According to their report, Patrick plans to formally announce Cowan's appointment at 11 a.m. this morning.)

Though described by CBS as "one of the best-kept secrets in town," Cowan's name surfaced two days ago in the Boston Globe. His impressive résumé explains why: he served as Deval Patrick's chief of staff after a career as an an attorney, and is involved with several Boston philanthropies.

Born in Yadkinville, N.C., Cowan, 43, is something of a fixture in Massachusetts politics. According to a 2010 Globe profile, he has worked with both Democrats and Republicans to increase the profile of racial minorities serving in government:

In nearly two decades in Boston, Cowan became a popular mentor for young black professionals and a talent scout frequently called upon to help diversify the city’s institutions. He helped Governor Mitt Romney, who faced criticism for the lack of diversity in his judicial picks, identify lawyers of color who would make good judges.

Cowan will abandon the seat in June after a special election determines a permanent replacement. He becomes the second black member of the Senate after South Carolina's Tim Scott was also appointed by his governor to fill a vacancy.