Rishi Sunak and Liz Truss may have to wait longer than they expected to find out who has won the Tory leadership race.
A YouGov poll on Tuesday put Ms Truss well ahead of the former Chancellor, with her lead among party members increasing to 34 points.
It shows 60 percent of the party members polled between July 29 and August 2 say they intend to vote for the Foreign Secretary, up from 49 percent since the period July 20 to 21.
Mr Sunak's support, meanwhile, has dropped from 31 percent to 26 percent.
The rest of the 1,043 membership polled say they are undecided or will not vote.
Tory leadership candidate Liz Truss
Finnbarr Webster
Rishi Sunak is hoping to take over as Conservative Party leader
Danny Lawson
It comes as the Tories delayed sending out ballots on the advice of the National Cyber Security Centre (NCSC), part of GCHQ, the Telegraph reported.
There was no specific threat from a hostile state and the concerns were instead raised over the vulnerability of the voting process, the report states.
Under the party’s original system members would be able to vote but change their decision while the ballot remained open, but now a unique code will reportedly be provided which will only allow one, unchangeable, vote.
The ballots had been due to be sent out from Monday, but could now arrive as late as Thursday August 11.
Given his polling struggles, the Sunak campaign will be hoping the additional time to make their case before the first votes are cast will fall in their favour.
The Truss campaign spent Tuesday performing damage control after abandoning a flagship policy to slash £8.8billion from public sector pay outside London.
The announcement on Monday night met fierce opposition from senior Conservatives who said it would be “levelling down” the nation by leaving nurses, police officers and teachers worse off.
Conservative Tees Valley mayor Ben Houchen, a supporter of Mr Sunak, said the proposed pay policy had left him “speechless”, and suggested it would have cost the party the next general election if implemented.
Mr Sunak’s camp argued that the move was no mistake, saying Ms Truss had called for the move when she was chief secretary to the Treasury in 2018.
But Ms Truss insisted her policy had been “misrepresented”.
Speaking to the BBC in Dorset, she said: “I’m afraid that my policy on this has been misrepresented. I never had any intention of changing the terms and conditions of teachers and nurses.
“But what I want to be clear about is I will not be going ahead with the regional pay boards, that is no longer my policy.”
A Liz Truss campaign source said on the YouGov polling: “Members are making up their mind, and they are supporting Liz.
“Her bold and ambitious plan for the country and economy is uniting Conservatives right across our nation. But we are certainly not complacent, Liz is fighting for every vote, meeting as many members as possible.”
An NCSC spokesperson said: “Defending UK democratic and electoral processes is a priority for the NCSC and we work closely with all parliamentary political parties, local authorities and MPs to provide cyber security guidance and support.
“As you would expect from the UK’s national cyber security authority we provided advice to the Conservative Party on security considerations for online leadership voting.”