If you spoke to most Conservative backbenchers during 2018, most would say Boris Johnson would never be prime minister. His time as foreign secretary was unimpressive; he was unserious, a liability. That changed dramatically over the following year, with the party in turmoil over Theresa May’s premiership and reeling from parliamentary Brexit rebellions. Johnson wooed MPs carefully, many over dinners hosted by Jacob Rees-Mogg. Over the course of the leadership election, he caught the momentum as the man who could get Brexit done and who could end the chaos. After the 2019 election, he was widely held as an electoral genius – although Dominic Cummings would have it that it was the strategy, not the man, that won it. But none of those factors ever really changed the doubts that many Conservative MPs had about Johnson. They support him because he is a winner, and only while he is. There have been moments in the pandemic that caused widespread discontent. Most MPs will cite the row over free school meals with Marcus Rashford, the disastrous algorithm that predicted exam results, the last-minute cancellation of Christmas, as some of the most embarrassing. But Johnson kept his party high in the polls, oversaw a successful vaccine rollout and won crucial byelections such as Hartlepool, and Old Bexley and Sidcup. However, since the Owen Paterson debacle and the attempt to make changes to the standards system that many MPs suspect were in order to save Johnson himself from a probe by the standards commissioner, the mood has notably darkened. The embarrassment of the No 10 Christmas party and the move to plan B within hours – seen by many as a diversion tactic – has turned grumblings to fury. It is not only sleaze. Over the past few months, Johnson has managed to enrage almost every wing of the party. Tax rises upset shire Tories; penalising poorer northern homeowners for social care funding upset MPs in the red wall; there have been rebellions on universal credit; internationalists were aghast at the chaos of the Afghanistan withdrawal – and there is widespread mutiny from libertarians over the move to plan B and Covid passports. Johnson could be left relying on Labour votes to push through the new measures. But is Johnson still ultimately a winner? One of the most immediate tests is the North Shropshire byelection next week, prompted by Paterson’s resignation after the fallout from his sanction for lobbying by the standards commissioner. The Liberal Democrats believe they have a strong chance of taking the seat, though Labour has also begun to campaign more in earnest, with local activists there affronted by suggestions that they should keep quiet in favour of the Lib Dems. A Lib Dem source said the party issue was coming up repeatedly on the doorsteps. “Many people in North Shropshire, including lifelong Tories, are furious about the No 10 Christmas party. “It is turning into a perfect storm for Boris Johnson, along with the NHS ambulance crisis, farmers being let down and rural communities feeling taken for granted. We were already closing in on the Conservatives in North Shropshire, but this has put rocket boosters under our campaign as we enter the final week.” Paterson’s majority was almost 23,000. The most likely scenario is that angry Tories stay at home in protest and give the Tories a reduced majority win. Most of Johnson’s colleagues will then move on and think “a win’s a win”, though doubts will linger. But if there is an upset like in Chesham and Amersham, Johnson could find himself at serious risk.