Complex sentence: Harper was originally from Ontario and a Liberal Party supporter, but in his early twenties he moved to Alberta, where he became involved in Progressive Conservative politics and then gradually in the formation of the new Reform Party, working as Reform's chief policy officer.
Split into simpler sentences: Harper was originally from Ontario and a Liberal Party supporter, but in his early twenties he moved to Alberta. He became involved in Progressive Conservative politics and then gradually in the formation of the new Reform Party, working as Reform's chief policy officer.