Complex sentence: He attempted on several occasions to win a seat for the CCF and then, its successor, the NDP either at the federal or provincial level before winning a seat in the Ontario legislature in the 1963 provincial election for the North York riding of Yorkview.
Split into simpler sentences: He attempted on several occasions to win a seat for the CCF and its successor, the New democratic Party (NDP) either at the federal or provincial level. He won election to the Legislative Assembly of Ontario legislature in the 1963 provincial election for the North York riding of Yorkview.