Complex sentence: In addition, the Labour Party polled more votes than National but failed to reduce National's numerical majority in Parliament; the country's First-past-the-post voting system enabled it to maintain a majority of 45 electorate seats.
Split into simpler sentences: In addition, the Labour Party polled more votes than National but failed to reduce National's numerical majority in Parliament. However, National was able to stay in power since the country's First-past-the-post voting system enabled it to maintain a majority of 45 electorate seats.