Complex sentence: Rochford and Southend East had a relatively marginal Conservative majority on its 1997 creation, as it had some of Labour's stronger wards in Southend, such as Kuursal and Victoria, though in the elections since a much larger majority suggests a Conservative safe seat.
Split into simpler sentences: Rochford and Southend East had a relatively marginal Conservative majority on its 1997 creation. In the elections since a much larger majority suggests a Conservative safe seat.