David Cameron faces his biggest by-election defeat yet at the hands of Ukip defector Douglas Carswell in Clacton.
The first poll of the constituency, which handed ex-Tory MP Carswell 53% of the vote in 2010, predicted he would be returned as Ukip's first elected candidate in Westminster with eye-watering support of 64%.
The Conservatives are trailing an enormous 44% behind on 20%, with Labour on 13%.
Survation's poll for the Mail on Sunday newspaper is a disaster for the Tories, who had made clear they planned to fight the seat vigorously following Carswell's shock defection on Thursday.
But Clacton had been viewed as a strong target for Ukip in 2015. Carswell himself had admitted to Politics.co.uk in 2013 he felt the seat only contained around one-third support for the Conservatives.
Now the Survation poll suggests a clear majority of 57% of Ukip supporters will back Carswell because they prefer his new party. One-third said they were prepared to support Ukip because of the candidate.
Carswell's decision to abandon the Conservatives does not seem to have hurt his reputation, with 49% labelling him a 'hero' and only 17% declaring him a 'traitor'.
Tory MPs have been quick to criticise their former colleague, suggesting his move is "counter-productive" because a Ukip vote increases the chances of Ed Miliband becoming prime minister.
Bob Neill, whose private member's bill guaranteeing an in-out referendum on EU membership is backed by the Tory leadership, told Politics.co.uk the by-election would be a "distraction" in the short-term.
"Splitting the vote of those who want to look afresh at our relationship with Europe is not helpful," he said.
"In the long-term, my bill is about concentrating the minds of general election [voters] that neither Douglas Carswell nor Nigel Farage are going to be prime minister.
"Ed Miliband or David Cameron are. Which one is going to deliver?"
Prominent eurosceptic John Baron said the Carswell defection was "unfortunate" because it "could create the impression we are divided".
He is among a number of Tory backbenchers identified as possible candidates for following Carswell in transferring their loyalties to Ukip.
But Baron told Politics.co.uk he was "disappointed" by Carswell's move and insisted he had no intention of changing sides.
Baron did call on the prime minister to adopt a clearer negotiating stance with Brussels, however.
"Given that only the Conservatives are going to be able to deliver a referendum in 2017 if they get elected, I think it's wise to flesh out some of the detail as to the sort of Europe we would want if we were in government," he said.
Cameron has held back from making specific demands on Brussels, in part because he hopes to secure the best possible job within the European Commission for Britain's nominee, Lord Hill.
Tory arguments against Ukip look like they will be unsuccessful because Clacton voters are surprisingly indifferent about the European Union debate.
Only 13% of Ukip supporters said they were worried by the EU. Six per cent voiced concern about cost-of-living issues, while five per cent were bothered by jobs.
Instead immigration emerged as the dominant problem for Clacton's Ukip supporters, 47% of which identified the issue as their main concern.
Meanwhile Liberal Democrats were expected to win just two per cent of support, putting Nick Clegg's party on course to lose its deposit in another by-election humiliation.
The polling data provides depressing reading for liberals for another reason, too. It puts Ukip on course to trump Simon Hughes' 44-point victory over Labour candidate Peter Tatchell in the 1983 Bermondsey by-election.