Complex sentence: Concurrently, PSOE leaders had tried to pressure IU into avoiding an electoral alliance with Podemos out of fear of being pushed into third place nationally, with some commenting that the party's actions had been erratic and confusing throughout negotiations.
Split into simpler sentences: Concurrently, PSOE leaders had tried to pressure IU into avoiding an electoral alliance with Podemos out of fear of being pushed into third place nationally. Some commented that the PSOE's actions had been erratic and confusing throughout negotiations.