If, as widely assumed, Liz Truss takes over from Boris Johnson, it will not just be the nation having to adjust. Labour must adapt at speed from an ideologically flexible prime minister happy to improvise, to one with a much clearer idea of what she wants. One thing is certain – Keir Starmer and his team will not underestimate an opponent they largely view as talented and hard-working. But Labour is also not short on ideas about how to combat her – she has been a minister for a decade, and shadow ministers have faced her in parliament in three different cabinet roles: justice, environment and foreign secretary. Truss is seen as a competent Commons performer, and Labour could also suffer from her status as the third Conservative prime minister who is a woman, when they have never had a permanent female leader. As shown in her interview on the BBC’s Laura Kuenssberg on Sunday, Truss can be adept in trying to shift an interrogation towards the subjects she wants to talk about. “She’s very good at confidently answering a question that she wasn’t asked,” said one Labour staffer who has helped shadow ministers take on Truss in other roles. “It’s a definite skill, and can work well in the Commons. But will it stand up to the scrutiny you get as prime minister?” While Truss’s public speaking has been sharpened by the Tory leadership contest for nearly two months, and comparisons to Theresa May’s sometimes robotic style are often unfair, she is nonetheless not as instinctive or adaptable as her two predecessors in the job, Johnson and David Cameron. “Johnson would just bluster through things, or even tell a blatant lie if needed,” the Labour staffer said. “With Truss you can see the wheels turning in her head. What you have with Truss is the maximum predictability.” One unknown is how all this would hold up under the much greater scrutiny she would face in No 10, and especially during the crucible of prime minister’s questions. A potential weakness perceived by some Labour aides is Truss’s occasional tendency to gloss over details, or even make mistakes and then either double down or blame others. “She’s got this weird tendency to dig in and say: ‘No, I meant to do that,’” the Labour staffer said. “Having found herself in a hole, she will stay in it, even as it fills with water. You can have that happen in little-known ways at the Ministry of Justice, or environment, or trade, but you can’t do that as prime minister.” Away from her presentational style, other Labour aides are poring over potential vulnerabilities in her appeal to the public, including whether Truss’s tendency to portray her comfortable middle class upbringing and education as somehow deprived could see voters conclude she is inauthentic. “If the first you heard of her is that she came from a rough school in Leeds and worked her way up, that can make a good impression,” one said. “But if you’re then told that’s not true, people think: ‘This is someone I can’t trust.’” Truss is also considered potentially vulnerable over ethical issues, with an apparent mistrust of scrutiny and a perceived habit of being opaque even over unimportant details. According to the government’s most recent transparency register, over a three-month period as foreign secretary, Truss declared just two meetings, with some cabinet colleagues logging 50 or more. But in what could feel like a return to the politics of several decades ago, Labour is likely to emphasise one thing above all else: Truss’s beliefs and her policies. In the Kuenssberg interview, Truss repeatedly stressed her utter belief in low taxes, a smaller state and minimal regulation, with her team talking about a “bonfire” of rules protecting workers. It is an economic platform more like Ronald Reagan even than Margaret Thatcher, bringing much more obvious dividing lines for Starmer than Johnson’s mix of boosterish populism and state-financed levelling up. “I do think that she is, at heart, the most ideological prime minister there has probably been in my lifetime,” a senior Labour source said. “She’s not going to be a ditherer. She’s going to try and smash things, which means we can’t just be on the sidelines saying: ‘Excuse me, what are you doing?’ “But we’re prepared for that. She’s clearly talented, and has something about her. There’s this weird thing that hers and Keir’s backgrounds are not completely dissimilar – state educated, smart people. So there’s a definite respect for her. “It’s just going to come down to the fact that we think she’s wrong about everything when it comes to policy.”