Complex sentence: Greene served as Chief of Staff in the office of then Reform Party of Canada leader Preston Manning from 1993 and 1996 and was an unsuccessful Reform Party candidate in Halifax in the 1993 and 1997 federal elections.
Split into simpler sentences: Greene served as Chief of Staff in the office of Reform Party of Canada leader Preston Manning for four years. He was an unsuccessful Reform Party candidate in Halifax in the 1993 and 1997 federal elections.