Complex sentence: In May 2015, he endorsed Sadiq Khan to be the Labour candidate for the 2016 London mayoral election, and in July then endorsed Jeremy Corbyn in the 2015 Labour Party leadership election.
Split into simpler sentences: In May 2015, he endorsed Sadiq Khan to be the Labour candidate for the 2016 London mayoral election. Livingstone backed Jeremy Corbyn in the 2015 Labour Party leadership election.