Kemi Badenoch could be forgiven for believing she had the perfect strategy to trip up Andy Burnham at their first PMQs clash.The day before, our new Prime Minister had stood at the despatch box for more than three hours to be grilled by MPs – primarily nervous ones from his own party – over everything from the state of Britain's high streets to soaring energy prices.And one eager-eyed Tory researcher had spotted an incriminating thing. Not once had Burnham rejected an opportunity to spend more public money.So the attack line was duly set. Warning of the ructions in the bond markets, Badenoch chided Burnham as a 'spendthrift Prime Minister' who 'wants to say yes to everyone' and is wedded to 'the same old Labour politics of tax and spend'.It seemed a good strategy – and the Leader of the Opposition prosecuted it with her usual verve.Except there was one problem. Andy Burnham is indeed a spendthrift. He does enjoy saying yes to everyone. He most definitely is, at heart, an old-school tax-and-spend socialist. And he doesn't care who knows it.For the past 30 years, Labour leaders have proven successful primarily when they have managed to convince people they are something they're not.Tony Blair won three elections by pretending not to be a leader of the Labour Party at all. Keir Starmer secured brief popularity by posing as the son of an Oxted toolmaker – and watched his fortunes implode when the country swiftly twigged he really was another ultra-liberal human rights lawyer.