Rishi Sunak faces a make-or-break week – but he isn’t master of his own fate

It’s another case of one step forward, two steps back for Rishi Sunak. After he enjoyed a rare good week, in which he created dividing lines with Labour on welfare reform, defence spending and his Rwanda scheme, Sunak’s momentum came to a sudden halt when Dan Poulter, the former health minister who is a part-time NHS mental health doctor, defected to Labour.

It was a symbolic reminder of the deep hole Sunak remains in, and that the real momentum remains with Labour. The Tories have regarded Poulter as semi-detached for a while, and assume he will be made a peer by Labour. He won’t trigger a by-election in his Central Suffolk and North Ipswich seat, but will stand down at the election and hopes to advise Labour on mental health.

For Sunak, the timing of Poulter’s move was terrible – and no doubt intended to be by Labour. Sunak needed a clear run on more favourable terrain up to Thursday’s local and mayoral elections in England, which were always going to make this a make-or-break week for the prime minister. The election results, with the Tories expecting to lose half of the 900 seats they are defending, offer Sunak’s right-wing critics the last realistic opportunity to oust him before the general election. Although a hard core of rebels might carry on plotting, they would be unlikely to win the backing of mainstream Tories for a putsch against Sunak if he survives the local election fallout.

Ministers tell me Sunak needs something positive to point to after Thursday’s contests, and that victory for either Ben Houchen, mayor of Tees Valley, or Andy Street, mayor of the West Midlands, would count. If both are defeated, and the Tories as expected lose the Blackpool South parliamentary by-election, then some allies admit Sunak will be in trouble. The rebels might then garner the votes of 52 Tory MPs needed to force a vote of confidence in Sunak as party leader.

Although he might survive such a vote, doing so would leave him wounded, as Theresa May and Boris Johnson were when they held on before being forced out later. While many Tories believe voters would think the Tories “mad” to change leaders yet again, a scenario in which Sunak suffers a haemorrhage of support among MPs currently loyal to him cannot entirely be ruled out. “If a vote is called, all bets are off,” one senior Tory admitted.

Right-wingers are drawing up plans to draft Penny Mordaunt, the Commons leader, as a caretaker leader for the general election. They claim she could enjoy a coronation as Michael Howard did before the 2005 election after a coup against Iain Duncan Smith. Voters would be spared the spectacle of a divisive Tory leadership contest, and the party would unite to take on Labour under a campaign called “100 days to save Britain”, according to right-wing plotters.

To win right-wing backing, Mordaunt would have to include right-wingers such as Suella Braverman and Robert Jenrick in her cabinet.

Two problems. Firstly, although her allies are said to have held talks with the rebels, Mordaunt told today’s Sunday Times that “further Westminster gymnastics and navel-gazing” would not serve the people.

“We’ve got to stick to the plan the prime minister has laid out.” Her words poured cold water on speculation she might resign from the cabinet.

Secondly, there’s a suspicion at Westminster that right-wingers are trying to use Mordaunt to oust Sunak as she would command the support of centrist Tories, and might then call the deal off, force a leadership contest and run their own candidate. Some right-wingers might not stomach Mordaunt’s socially liberal instincts on issues such as trans rights.

The very existence of such plotting is debilitating for Sunak, and makes it harder for him to keep the spotlight where he wants: on “the choice” between his party and Labour.

To do that, he must first see off his enemies within. The nuclear weapon in his locker is the timing of the general election. Rumours have swirled that he might announce one as early as tomorrow to head off a confidence vote after the local elections. The speculation has been fuelled by Labour, which likes talking up a snap election so it can then accuse Sunak of “bottling” it.

However, Sunak might need to at least threaten a summer poll if the rebels pose a serious threat to him after Thursday’s results. Interviewed on Sky’s Sunday Morning with Trevor Phillips programme, he declined to rule out a July election. “I’m not going to do that,” he said.

Downing Street is also believed to have pencilled in 27 June as a possible election date. Such fallback plans are designed to calm fractious Tory MPs, most of whom want to wait until the autumn.

For now, I think an October or November contest remains much more likely. But as he starts what could become his most testing week as prime minister, Sunak knows that he is not master of his own fate, and that events could soon spiral out of his control.