Complex sentence: Juan Carlos Rodríguez Ibarra was able to be re-elected for a fourth term in office thanks to the abstention of IU, as both PP and IU commanded the absolute majority of seats and could potentially block the PSOE in the Assembly, as had happened in Andalusia.
Split into simpler sentences: Juan Carlos Rodríguez Ibarra was able to be re-elected for a fourth term in office thanks to the abstention of IU. Both PP and IU together commanded an absolute majority of seats and could potentially block the PSOE in the Assembly, as had happened in Andalusia.