Labour is “throwing the kitchen sink” at claiming the Conservative stronghold of Selby and Ainsty, amid growing optimism that it can pull off a shock win that would show its progress in Tory-held rural seats. The North Yorkshire constituency, which was recently vacated by Boris Johnson ally Nigel Adams, returned a majority of more than 20,000 for the Tories at the last election. Labour had been targeting a strong second place in the seat, to fend off claims that only the Liberal Democrats can take on the Tories in their heartlands. However, while Labour officials believe the campaign will be defined over the final 10 days before polling day, early reports from the byelection campaign have raised hopes that the party has a chance of an unlikely win. Labour is already expected to win another byelection in Uxbridge and South Ruislip, the seat vacated by Johnson, where the majority at the last election was just 7,210 votes. Senior officials have opted to provide resources for the Selby campaign on a similar footing to Uxbridge before the ballots on 20 July. A series of shadow cabinet ministers are being dispatched to the seat, including Rachel Reeves and Emily Thornberry in the last week. The news comes with figures around Keir Starmer frustrated by assumptions that the Lib Dems would be the biggest threat in Selby and other rural seats. Labour is also planning a full assault on Mid Bedfordshire, another largely rural seat that former culture secretary Nadine Dorries has promised to vacate. She has not yet formally resigned. Insiders believe proving that Labour is making progress far outside its heartlands is a crucial step before next year’s general election. However, the degree to which hardened Tory voters opt not to turn out at the Selby byelection is seen as the potentially crucial factor in the outcome. “It’s not a constituency we’ve ever held,” said a senior figure. “The seat as it’s constructed right now would never have been Labour in any kind of general election challenge. But it’s going well. Whether it’s going well enough to win, it’s just so hard to tell. “We’re putting resources into both [Uxbridge and Selby] and we’re in a fortunate position where we can have good staff, MPs and organisers and activists into both. Our aim at the start in Selby was to show that we can give ourselves a chance to win the redrawn seat at the general election. “But we also want to show in this campaign that Labour can win votes in rural parts of the country directly off the Tories. I think that’s what will happen in Selby - whether it’s enough or not, we’ll have to see. For us, it’s a sort of a no-lose situation. We can throw the kitchen sink at it.” The byelections now pose a huge problem for Rishi Sunak, who has seen Labour’s poll lead widen in recent weeks after initially improving his party’s standing in the wake of Liz Truss’s calamitous time in office. Sunak headed to the Selby and Ainsty seat today [SAT] as he attempts to see off Labour’s challenge. A recent poll suggested Labour had a 12-point lead in Selby, with 41% backing Labour’s Keir Mather and 29% supporting the Conservatives’ Claire Holmes. It would represent a swing of 24 points from the Tories to Labour if repeated on polling day. Meanwhile, Labour officials have become nervous about the Uxbridge race after losing a local council byelection in Cambridge to the Conservatives last week. The campaign was dominated by a plan to introduce a congestion charge. The Tories have not had a councillor in Cambridge since 2012. In the last few days, Labour’s Uxbridge candidate, Danny Beales, has spoken out against London mayor Sadiq Khan’s plans to expand the capital’s ultra-low emission zone (Ulez) to the constituency. The disagreement has been seized on by the Tories, who are effectively trying to turn the race into a single-issue contest. Beales said last week that it was “not the right time” to extend the Ulez scheme. His intervention appears to have been sanctioned by the leader’s office, which is desperate to secure the symbolism of winning Johnson’s former constituency. “You can see that if you get the politics wrong, even if the polls are good, you can do very badly,” said one figure involved in the byelection campaigns. “Both Selby and Uxbridge present different challenges – Uxbridge because of Ulez and Selby because of how many core Tory votes are out there and how rural the constituency is, which makes it very hard for us to cover in a short campaign.”