YouGov pollster Wells said that if younger voters turned out on election day, then May could win a much smaller majority than initially predicted or even lose her majority. Just under a third - 30 per cent of people say they would prefer the Labour leader as prime minister to 43 per cent backing May.
But the 20-point opinion poll lead of the time is now into single figures. "But the Conservatives' lead has more than halved in recent polls", Kallum Pickering, senior United Kingdom economist at Berenberg, said in a note.
"Furthermore, it would only take a slight fall in Labour's share and a slight increase in the Conservatives' to see Theresa May returning to Number 10 with a healthy majority".
But despite starting off strongly ahead in polls, the Conservative Party has been losing ground in recent days.
But if she fails to beat the 12-seat majority her predecessor David Cameron won in 2015, her electoral gamble will have failed and her authority will be seriously undermined.More news: Murray and Wawrinka sweep into French Open last 16
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YouGov firm acknowledged that its predictions were controversial and that they suggested big swings in the usual voting patterns for many Britons.
"This was not a poll, rather it is the outcome of a model that has used untested methodology to come up with this hung parliament conclusion", she said.
What can not go up, must go down. the YouGov poll already sent GBP/USD back down under 1.28.
But the pound proved resilient on the news, falling just 0.2% against the dollar to $1.287.
"There is a slightly more cautious attitude as a result of those narrowing polls", said Michael Hewson, chief market analyst at CMC Markets.
He added: "This has been the general pattern of general elections for an age, and whether you believe our poll findings or those of others will depend on whether or not you think Jeremy Corbyn can actually buck that trend". "The prime minister seems to have difficulties in meeting anyone or having a debate", Corbyn said. Instead, May sent her interior minister, Amber Rudd, who dismissed the leaders as members of a "coalition of chaos".
Rebutting questions from journalists during a visit to factory workers in Bath, southwest England, May denied she was scared of the scrutiny. While both politicians have managed to keep their cool during the debate, both have also shown discomfort under hard questioning.