Complex sentence: This was a reversal of the situation at the national level; in Queensland, the Country Party had historically been the larger of the two non-Labor parties and had been senior partner in the Coalition since 1925.
Split into simpler sentences: This was a reversal of the situation at the national level. As a result, the Country Party had historically been the larger of the two non-Labor parties, and had been senior partner in the Coalition since 1925.