The foreign secretary is now the bookies’ favourite to be Britain’s next prime minister after rival Penny Mordaunt was eliminated in the final round of voting by the party’s MPs.
The former No 10 strategist, who masterminded the Leave campaign, scoffed at the European Research Group (ERG) for getting behind Truss in her surge past Mordaunt.
“Totally on-brand for ERG to back a truly useless Remainer who did nothing in govt except gabble with hacks cos she’s reassuringly mad behind the eyes,” Cummings tweeted.
Boris Johnson’s ex-adviser turned nemisis also claimed the PM quietly supported Truss’ campaign because he “knows she’s mad and thinks she’ll blow and he can make a comeback”.
Cummings said his former boss’s immediate priority was stopping Sunak. But he added: “He knows Truss is mad as a box of snakes and is thinking, ‘There’s a chance she blows, there’s another contest and I can return’.”
Cummings said he had given the foreign secretary the nickname “human handgrenade” because she “caused chaos rather instead of getting things done”.
He also mocked Truss’ celebratory tweet after the final round of parliamentary results when she said: “I’m ready to hit the ground from day one.”
Cummings responded: “Sure would ‘hit the ground’ and she wouldn’t bounce much. Splat, for Tories and UK.”
The foreign secretary later deleted the tweet and replaced it with the message: “I’m ready to hit the ground running from day one.”
After leading the race to succeed from the start, Rishi Sunak held onto his first place with 137 MPs’ votes when the final round was announced on Wednesday afternoon.
But Ms Mordaunt, second in the four previous rounds of voting, was dramatically overtaken at the last minute by Ms Truss, who took 113 votes to the trade minister’s 105.
The group of 40 to 50 MPs in the ERG had been split on which Tory candidate to back. But many are believed to have gone to the foreign secretary after ardent Brexiteer Suella Braverman was defeated at an earlier round in the race.
Stoke MP Jonathan Gullis, who came out for Truss earlier on Wednesday, said he did so because “despite being a Remainer, she talks toughest on Brexit”.
The most recent ConservativeHome online survey of the Tory grassroots suggested that Truss would beat Sunak in a head-to-contest contest decided by members.
However, Sunak set out his pitch to members in a brief video clip claiming that he is “the only candidate” who can beat Keir Starmer and Labour at the next general election.
Meanwhile, the former chancellor’s allies have rejected the idea that his camp “lent” or reallocated votes other candidates.
There have been claims by Mordant’s allies that votes were lent to Truss because Sunak preferred the idea of facing her in the run-off.
“We’ve been trying to maximise the vote for Rishi Sunak,” Tory MP John Glen told the BBC. And Tory MP Gavin Williamson – asked by reporters if he had helped “lend” votes to others – said: “I don’t know what you’re talking about.”
A source in the Sunak camp said accusations that his team had encouraged supporters to vote tactically to ensure a run-off with Ms Truss were “absolutely not true”.
“It’s a very strong lead over the second-placed candidate, Liz. I think we’re content with that. Everybody who wanted to see Rishi through voted for him, there was a significant rise in our vote compared with yesterday.”