On 8 May 2015, the day after the Labour Party lost the general election, Watson announced his intention to stand in the ensuing deputy leadership election, becoming the first to declare. Watson was nominated by 59 Members of Parliament, more than any other candidate, and quickly emerged as the front runner. On 12 September he was elected as Deputy Leader of the Labour Party with 198,962 votes or 50.7% in the third round, including second preference votes from those who voted for other candidates. He was also appointed Chairman of the Labour Party and Shadow Minister for the Cabinet Office by new Labour leader Jeremy Corbyn. In 2019 after he stood down both as an MP and as Deputy Leader he said he had voted for Owen Smith in the 2016 Leadership election.