When May called the snap June 8 election at the beginning of March, the Conservative Party led Labour by some 20 points in most opinion polls. The opposition Labour party, led by veteran socialist Jeremy Corbyn, has gradually nibbled away at the Conservative lead in the polls, with the campaign back in full swing after the Manchester terror attack.
That would raise questions about the future of Brexit, Britain's $2.5 trillion economy and British policy on a range of issues including corporate taxation and government spending and borrowing.
Betfair Spokesperson, Katie Baylis, said:"There's no doubt Labour are closing the gap in the polls, which is a sentiment that's also being reflected in the odds and it seems Corbyn gave his Labour party a slight advantage after last night's "debate" with the party's odds shortening into 11/1 from 13/1 yesterday on the "Most Seats" market".
Political uncertainty has had less of a direct impact on the FTSE 100 which posted a 4.5 percent gain in May, its best monthly showing this year.
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But despite the unpopularity of the proposal, May is more than 10 points ahead of Corbyn (43 versus 30) in personality ratings.
But its chief executive, Stephan Shakespeare, told The Times that the model had been tested during the run-up to the European Union membership referendum past year when it consistently put the Leave campaign in the lead.
Campaigning in the city of Bath in England's West Country, May was asked about the YouGov poll which dominated the front page of the Times newspaper in London. "And even if his promises are practically impossible and economically catastrophic, set against the Tories' unnecessarily defensive campaign it's small wonder he appears to be picking up support".
Corbyn and Farron were joined by the leaders of the Green party, the UK Independence Party and Welsh nationalists Plaid Cymru and the deputy leader of the Scottish National Party.
The latest YouGov/ Time voting intention survey shows that support for the Conservatives declined markedly to 42% while the Labours gained +3 points to 39%.