The Liberal Democrats became the new favourites to win the North Shropshire by-election next Thursday as the backlash against Boris Johnson's Conservatives continued following footage of his aides laughing about a Christmas party in Downing Street last December.
The by-election, which will arrive at a bad time for Johnson as he comes under immense pressure, is taking place in what has been a safe Tory seat.
Lib Dems go odds-on to pull off spectacular upset
Owen Paterson, who resigned over allegations of sleaze, held the constituency for the Conservatives since 1997. Two years ago, they won almost 63% of the vote, with Labour coming second and the Liberal Democrats third.
The Lib Dems have shortened to 1.9520/21 on the Betfair Exchange but they have been backed at longer than 6.511/2.
Last month, shortly after the date for the by-election was set, the Conservatives were 1.330/100 on the Sportsbook.
Last week, the Conservatives held on to Old Bexley and Sidcup but their majority was slashed in a by-election that saw a swing to Labour of over 10%.
North Shropshire looks like it could produce an upset to go alongside the one the Lib Dems pulled off in Chesham and Amersham earlier this year when they took what had been a safe Tory seat.
There has been a concerted campaign in the anti-Tory press to persuade Labour supporters to vote tactically and get behind the Lib Dem candidate.
With a previously safe seat, the Tories would usually be expected to put everything into holding on in North Shropshire with visits to the constituency from senior figures. But the sight of Johnson, at a time when the backlash is growing about the Christmas party in Downing Street, could do more harm than good.
In the past 24 hours, the odds on the PM leaving office this year were slashed from 149/1 to 7/1.
He endured a torrid PMQs, receiving criticism from all sides of the Commons, and more allegations are emerging at the time of writing.