Complex sentence: The Commonwealth's senior member of the United States Senate, elected in 2012, is Elizabeth Warren, defeating incumbent Republican Scott Brown who had been elected in 2010 after the death of Ted Kennedy.
Split into simpler sentences: The Commonwealth's senior member of the United States Senate, elected in 2012, is Elizabeth Warren. Warren defeated incumbent Republican Senator Scott Brown who had won a special election in 2010 to win the seat after the death of Ted Kennedy.