In August, a Conservative Home poll found Mr Sunak was the most favoured to move from No11 to No10. But now, the Chancellor has dropped down the rankings in a new poll, with Ms Truss – who took on Brexit negotiations last week – surging past him.
According to the new poll, Ms Truss is leading 23 percent (181 votes) to Mr Sunak’s 20 percent (161) in the self-selected survey of Tory members.
The poll – which surveyed 786 Britons – found Penny Mordaunt was third to take over from Boris Johnson with just 8 percent of the votes.
Although Mr Sunak has dropped down in the Conservative Home poll, the Chancellor is still favourite to take over in the betting market.
According to a survey by Oddschecker, the Chancellor has a 32 percent chance of being the next leader, while Ms Truss has 17 percent chance.
Mr Sunak’s drop in popularity may come after he unveiled a free-spending Budget which chose to “invest” rather than “retrench” after the coronavirus pandemic battered the country last month.
According to his budget, departmental spending will go up by £150 billion over the current parliament.
This is an average of 3.8 percent a year.
Last month, Mr Sunak received 10 percent of votes in an Express.co.uk poll – which surveyed 14.509 people – asking which candidate would be best to replace Mr Johnson.
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Mr Johnson is facing increasing pressure after it was revealed there were several parties in Downing Street during the coronavirus pandemic.
At the time of one of the Christmas party, London was subject to tier 3 restrictions, which imposed a ban on social mixing between households.
No 10 initially did not say the reports were inaccurate but said all rules had been followed, before later denying any party had taken place, despite leaked footage emerging.
Mr Johnson told the Commons that Downing Street staff reiterated “there was no party and that no Covid rules were broken”.
He added if lockdown rules had been broken, “then there will be disciplinary action for all those involved”.
Speaking during Prime Minister’s Questions on December 8, he said: “I understand and share the anger up and down the country at seeing No 10 staff seeming to make light of lockdown measures.
“I can understand how infuriating it must be to think that people who have been setting the rules have not been following the rules because I was also furious to see that clip.”
The SNP’s Westminster leader Ian Blackford called on Mr Johnson to resign after the news broke.
Allegra Stratton – the former spokesperson for the Prime Minister – resigned after footage was leaked of her preparing to answer questions about the parties.
Another video shows House of Commons leader Jacob Rees Mogg addressing the party saying they will not be investigated by the Met Police in a year’s time.