The Foreign Secretary’s team is said to be in talks with a number of Mr Sunak’s backers and claiming some notable politicians could publicly change sides this month.
“We are staying in contact with MPs of all stripes, including some Rishi supporters, to try to convince them to come over,” a Truss campaign source told The Telegraph.
The move is an attempt to dent one of Mr Sunak’s strengths in the campaign – that he has the support of more of the 358 Conservative MPs than Ms Truss.
The Sunak campaign believes the advantage is helping them win over Tory members because of the influence MPs have in their constituencies.
Truss campaign figures have not provided the names of individuals allegedly considering switching, making the claim hard to verify independently.
But they have had at least one notable success outside Westminster in convincing people to change allegiances in the race. James Evans, the Tory representative for Brecon and Radnorshire in the Welsh Parliament, switched from Mr Sunak to Ms Truss on Wednesday, the day on which the Cardiff leadership hustings were held.
At the start of the Leadership contest I was backing Rishi but as this has gone on there is only one person to unite the country and the party and that is Liz Truss! 🏴 pic.twitter.com/EcMkdYRabt
— James Evans MS (@JamesEvansMS) August 3, 2022
There could be a political incentive for MPs to switch sides, with Ms Truss, the Foreign Secretary, having a lead of more than 30 percentage points in two recent opinion polls of Tory members.
The winner will decide which MPs become government ministers – a factor throughout the contest as Tory parliamentarians have weighed up who to back. Many of the MPs appointed to Boris Johnson’s first Cabinet backed him in the 2019 leadership race.
The rush of recent high-profile endorsements – four former Tory leadership rivals have backed Ms Truss in the last week – suggests some see political advantage in going public with support now.
Sajid Javid became the latest to back Ms Truss, following Nadhim Zahawi, the Chancellor, Penny Mordaunt, the trade minister, and Tom Tugendhat, the chairman of the Commons foreign affairs committee.
Mr Javid, the former chancellor and health secretary, had been in charge of the Treasury when Mr Sunak was effectively his deputy, holding the role of chief secretary to the Treasury. The pair were believed to have been politically and personally close.
In an interview on Thursday morning, Mr Javid said: “I think Liz is best placed to unite the party, to fix the economy and to beat Labour at the next election.”
Announcing his endorsement on Wednesday, he wrote in The Times: “With only two years before the next election, there has been a temptation to just ‘get the barnacles off the boat’ and avoid any short-term political pain for long-term national gain. We must reject that.
“As a nation, we are sleepwalking into a big-state, high-tax, low-growth, social democratic model which risks us becoming a middle-income economy by the 2030s with the loss of global influence and power.”