Rishi Sunak has vowed to carry on as an MP despite losing the Conservative leadership race, with supporters suggesting his better than expected performance means he could run again if Liz Truss loses the next general election. The Guardian understands he told party donors at an event the day before voting closed last week that he would remain in frontline politics regardless of the result. Allies close to the former chancellor confirmed he planned to fulfil that pledge and not quit parliament, which would have triggered an early and potentially embarrassing byelection for Truss in his Yorkshire constituency of Richmond. Sunak received 43% of the vote from Tory members and sources on his campaign claimed they had won over a high proportion of members who remained undecided until the final weeks of the contest. The former chancellor is will not be offered a cabinet job after he declined to say last month whether he would vote for an emergency Truss budget. Tory sources also said he would likely have rejected the offer of running a “poisoned chalice” department, such as the Department of Health and Social Care, for which the Sun previously reported that he was being lined up. Some have suggested the wealthy Sunak could have his eye on a return to a career in banking. Speculation about his departure from Westminster also grew over the weekend when he failed to promise that he would run as an MP at the next election – saying it would be “presumptuous” to assume he would be selected again by his local association. But Sunak told donors at a private event with Truss last Thursday that he would remain in frontline politics, to rapturous applause from those present, sources said. In an interview on Monday with the BBC, he said he was “very committed” to his constituents and added: “I don’t plan on going anywhere.” His supporters also said the former chancellor would spend the next few years lurking on the backbenches. They claimed he wanted to “wait it out” and “be able to say ‘I told you so’” if the economic consequences that Sunak warned Truss’s plans would lead to come to pass. During the campaign, he claimed her tax cuts would fuel inflation and benefit the better-off. If he is proved right and Truss fails to recover the Conservatives’ dire poll ratings, Sunak’s supporters said he would be well placed to lead the party through its first spell in opposition in at least 12 years. Nevertheless, they realise Boris Johnson could also be weighing up another run for the top job. Sunak’s allies insisted he would be loyal to Truss and avoid making interventions designed to wound her – at least during her honeymoon period. Even one Truss-supporting MP admitted Sunak might get lucky by waiting in the wings. “He could hang around until when the next election is called and see which way the wind is blowing,” they said. “If we lose, the party will have to face up to reality and should be more willing to listen to his hard truths.” Nevertheless, a number of Sunak’s backers think he would fare similarly to Jeremy Hunt – who made it to the final two of the leadership contest in 2019 but was ejected in the first round of voting by MPs this time around. “He’s no longer going to be ‘the next big, bright young thing,” one said. Though there is a scarcity of Sunak supporters said to be in line for senior roles in Truss’s cabinet, her allies insist they will still be given minister of state posts.