Boris Johnson is at risk of losing two key by-elections taking place today, according to a leading pollster.
Professor Sir John Curtice said should regain Wakefield, which they lost to the Conservatives at the last general election in 2019.
Meanwhile, the Lib Dems could overturn the Tories’ 24,000 majority in Tiverton and Honiton if enough Labour voters decide to give them their vote this time around.
It would be the first time in 30 years since a sitting prime minister has suffered a double by-election defeat on the same day.
Writing in The Independent, Curtice said: “A swing of a little less than 4 per cent from Conservative to Labour [in Wakefield] would be sufficient for Sir Keir Starmer to reclaim the seat and register his party’s first by-election gain under his leadership.
“Labour ought to have little difficulty in surmounting this hurdle.”
However, the polling expert said Labour need to win by around 20 points - a swing of around 14 per cent since 2019 - to show they are on course for government at the next election.
One shadow cabinet minister told HuffPost UK that he expects the party to win by between 3,000 and 4,000 votes “or 5,000 on a good night”.
The picture is less clear in Tiverton and Honiton, Curtice said, although the Lib Dems have a very good chance of pulling off a stunning victory.
“Success will depend not only [the Lib Dems’] ability to garner the support of dissatisfied Conservatives but also the tactical support of those who would otherwise vote Labour,” he said.
“Whether or not Labour’s vote collapses to the benefit of the Liberal Democrats, as it did both in North Shropshire and in the Liberal Democrats’ other by-election success a year ago in Chesham and Amersham, could well be crucial to the outcome.”
One Lib Dem activist told HuffPost UK: “Some think we will probably get over 50 per cent and the Tories less than 35 per cent.”
They also said the party’s ground game could also prove crucial.
“I drove through the constituency and spotted at least 10 Lib Dem posters and only one Tory and one Labour.”
Lib Dem leader Ed Davey is guarding against any complacency, however, insisting that the race is “neck and neck”.
“This is a once in a generation chance to end years of neglect and get a better deal for Devon, by backing the Liberal Democrats,” he said.
“We could be on the verge of a historic victory, but it is now neck and neck between the Liberal Democrats and the Conservatives and every vote will count.”
The fact that by-elections are being held due to Tory scandals could also work against the prime minister.
Imran Ahmad Khan quit as Wakefield MP after being convicted of sexually assaulting a teenage boy, while Neil Parish resigned as the Tory MP in Tiverton and Honiton after he admitted watching porn in the Commons.
Despite winning a vote of confidence in his leadership less than two weeks ago, a double by-election defeat would also raise fresh questions about the PM’s future.
However, Johnson would miss any immediate fallout from the results as he is attending the Commonwealth heads of government summit in Rwanda.