Democrats in Ohio are learning lessons from Britain's Brexit vote amid fears supporters might not turn out to vote if Hillary Clinton is favourite to win.

David Pepper, the chairman of the Ohio Democratic Party in one of the key US election battlegrounds, drew parallels between Britain's European Union referendum and the hotly contested race for the White House.

He said that Brexit had 'snuck up on people', and he suspected the Mrs Clinton's national campaign team in Brooklyn were examining what had happened in the United Kingdom.

'The number one lesson would be don't let anyone get overconfident or lax and therefore not turn up.'

Mrs Clinton made it clear through a former policy advisor that she backed Britain's continued membership of the European Union, and President Barack Obama also intervened during Britain's European Union campaign, telling a press conference Britain would be at the back of a queue on a trade deal.

Mr Pepper said: 'Three weeks ago there was a sense this was going to be a runaway and Trump was going to lose everywhere. I was worried that then that we might have what happened with Brexit where people didn't think they needed to vote. As much as the last week hasn't been that fun, the one thing I can tell you is people are showing up.' In Ohio, it is key that the Democrats get their votes out in major cities to offset rural areas where people are more likely to vote for the Republicans. He said they needed to run up big numbers in places like Columbus and Cincinnati.

But he said that millennials - a term used to described under 35s - would be key.

Polls suggested that in the UK, the under 35s were more likely to vote for Brexit, but the age group also showed the lowest turnout.

'If Hillary Clinton wins, it will be because the millennials are so much more supportive of her than Donald Trump. Everything Donald Trump stands for is scaring the millennials - it's sort of like that Brexit vote. They are very turned off by Donald Trump.'

He said that the Clinton campaign had spent a year getting organised for the last five days of the campaign and the 'basic game plan' was to have thousands of volunteers organised enough to show up at thousands and thousands of doors and make thousands of phone calls to make sure people actually turn up and vote.

Millions of dollars have been spent by the Clinton campaign on paying for a large staff to get people out to vote.

Mr Pepper said he thought the Donald Trump campaign was trying to play catch up as they had not been following the 'fundamental way of running a campaign'.