Donald Trump's national political director has announced he is "stepping back" from the campaign - the day after a final presidential debate which many Republicans saw as Mr Trump blowing his final chance at electoral victory.

Jim Murphy, who joined the team in June, told Politico that he was leaving the campaign for personal reasons.

"I have not resigned but for personal reasons have had to take a step back from the campaign," he told the site.

Mr Murphy was described by Politico as a longtime party operative, who played a key role in setting up field programmes in battleground states.