Labour and the Conservatives are neck and neck in the battle for the previously safe Tory seat of Mid Bedfordshire, according to a poll that suggests a split “progressive” vote could allow Rishi Sunak’s party to retain the constituency. Labour and the Liberal Democrats are making a full-tilt effort to win the seat from the Conservatives after the resignation of Nadine Dorries, a close ally of Boris Johnson, who eventually quit after being denied a place on the former prime minister’s resignation honours list. A new constituency poll seen by the Observer suggests that the Tory vote share in the seat has collapsed, halving from the near 60% that Dorries enjoyed at the last election. However, the Survation poll commissioned by the Labour Together group, which is close to Keir Starmer, has Labour and the Tories on level pegging. With undecided voters excluded, it puts Labour candidate Alistair Strathern and the Conservative candidate, Festus Akinbusoye, on 29% of the vote each. It would represent a double-digit swing from the Conservatives to Labour since the election. However, the Lib Dem’s Emma Holland-Lindsay is a close third, with 22%. With undecided voters included, Labour and the Conservatives are tied on 20%, with the Lib Dems on 15%. The poll found that 27% of those intending to vote are still undecided. The three-way split means that senior figures in Labour and the Lib Dems are well aware of the possibility that they could allow the Tories to win the seat, despite a halving of their vote share. Labour Together said the poll showed almost a third of voters (29%) will be voting tactically. Labour supporters immediately seized on the results of the poll to argue that the party had emerged as the main challenger. Josh Simons, director of Labour Together, said: “Our polling clearly shows this is a two-horse race between Labour and the Conservatives. After 13 years, Britain needs the Conservatives out and Keir Starmer’s Labour in. Voting Labour is the best and only way for voters in Mid Bedfordshire to send a message to this shambolic Tory government.” Labour is desperate to do well in the seat to prove it can win in the Tory heartlands. Strategists also believe a changing demographic in the seat’s many villages and new-builds gives it a chance. The Lib Dems argue that they have a track record of overturning big Tory majorities, pointing to their byelection triumphs of recent years, such as in Somerton and Frome. While constituency-level polls can be hard to conduct, the results are similar to an Opinium poll in the seat conducted in June, which had Labour on 28%, the Tories on 24% and the Lib Dems on 15%. The apparent closeness of the race means the success of the smaller parties could also play a role. Gareth Mackey, a well-known independent candidate, has 6% support and Reform UK has 7%, according to the latest poll. Survation contacted 559 respondents between 12 and 14 September, of whom 481 were contacted by telephone, with 78 from a younger age group targeted online. Damian Lyons Lowe, chief executive of Survation, said: “The manner that tactical voting plays out looks certain to determine whether the Conservatives can cling on or not. “On the one hand, the polling shows that the Liberal Democrats have done a slightly better job in attracting 2019 Conservative voters than has Labour. However, the party has the challenge of coming from a smaller base of prior support – just 13% of Mid Beds voted Lib Dem in 2019, compared with 22% of the constituency voting Labour. “Were this election to be held tomorrow, Labour’s neck-and-neck polling status with the Conservatives makes a tactical Labour vote look more sensible to defeat the Conservatives here. “Labour will no doubt take heart in these polling figures that a Mid Beds victory looks highly credible in a seat where the party finished almost 25,000 votes behind the Conservatives in 2019. The Lib Dem byelection machine, however, is unlikely to be discouraged.” A Lib Dem source insisted it was a “devastating poll for Labour” because its vote share had not increased significantly since the last constituency poll. “This poll confirms Conservative voters are turning to us, not Labour,” they said. “It’s clearer than ever that the Lib Dems are best placed to beat the Conservatives in rural Mid Bedfordshire. When even Labour’s own polling shows that, you know they are in trouble.”