Complex sentence: Other key factors had been the contrast in conferences of the Green Party and Labour in September 2014, and the media exclusion of the Greens during and following their successes in the European elections; a petition against the media blackout of the Green Party reached 260,000 signatures.
Split into simpler sentences: Other key factors had been the contrast in conferences of the Green Party and Labour in September 2014, and the media exclusion of the Green Party during and following their successes in the European elections. A petition against the media blackout of the Green Party reached 260,000 signatures.