WASHINGTON, D.C. -- The man chosen to serve as interim U.S. Senator in Massachusetts has officially been sworn in by Vice President Joe Biden.
Last week, Massachusetts Governor Deval Patrick selected William "Mo" Cowan to replace John Kerry. Kerry is now serving as Secretary of State.
Cowan worked for Governor Patrick as chief of staff and legal counsel, and before that, he was a partner in a Boston law firm.
Cowan will hold the position until a special election on June 25th.