Complex sentence: For some years opinion polls had suggested that a majority of the electorate favoured a republic, but the republic referendum was nonetheless comfortably defeated due to sustained opposition from monarchist groups, and division amongst republicans on the method proposed for selection of the president.
Split into simpler sentences: For some years opinion polls had suggested that a majority of the electorate favoured a republic. Nonetheless, the republic referendum was comfortably defeated due to sustained opposition from monarchist groups and to division among republicans on the method proposed for selection of the president.