The Conservative leadership contest has been distinctively marked by a deluge of “blue-on-blue” infighting, leaving many wondering whether the new prime minister will be able to unite the party before the next general election.
Tory attacks have become increasingly brutal since Ms Truss and Mr Sunak secured their places on the final ballot over a month ago.
The two have passionately clashed over tax, foreign affairs and how to tackle the cost-of-living crisis.
Supporters of both sides have also dished out criticism of their opponents during the campaign, with some not only condemning policies but also tweeting bruising personal attacks.
In a sign of irreconcilable differences between the two rivals, the former chancellor recently hinted he would not take a cabinet post if Ms Truss wins the race, explaining ministers “need to agree on the big things”.
Mr Sunak reportedly decided to quit Boris Johnson’s Cabinet over how and when to cut taxes.
Asked about reports he could be in line for health secretary if Ms Truss beats him to become the next prime minister, the former chancellor told BBC Radio 2: “I am not focused on all of that and I doubt Liz is. I am not thinking about jobs for me or anyone else.”
He added: “One thing I have reflected on a bit being in government and cabinet [is] you really need to agree on the big things because it’s tough, I found, if you don’t.
“I wouldn’t want to get into a situation like that again.”
The “big things” mentioned by Mr Sunak include how to deal with the cost-of-living crisis and, more generally, tax policy.
During the first television debate, Mr Sunak interrupted the Foreign Secretary around 25 times and accused her of “unconservative and unfunded” plans to cut taxes.
Meanwhile, Ms Truss has branded Mr Sunak’s policies “Gordon Brown economics” and has repeatedly said they would “crash the economy” and lead to a recession.
Mr Sunak’s campaign team have also attacked Ms Truss for focusing on tax cuts and, at first, ruling out handouts to help struggling families with energy bills.
Ms Truss has argued that tax cuts will help to grow the UK’s economy.
Her team have not ruled out providing further help to people this winter, but said they will not reveal what she will do until the leadership contest is over, on September 5.
Having an emergency budget next month – in which Ms Truss plans to make long-term funding pledges if she becomes prime minister – had been a key part of the Foreign Secretary’s campaign to get into No 10.
But this has now been downgraded to a promise of a “fiscal event” after a row over whether she would have to wait for official economic forecasts by the Office for Budget Responsibility (OBR) to be completed before announcing new measures.
The leadership race has also seen Sunak and Truss supporters involved in social media spats, with Tory MPs accusing each other of “hypocrisy”.
Culture Secretary Nadine Dorries, a high-profile supporter of Ms Truss, landed in hot waters after sharing a doctored image on Twitter that portrayed Mr Johnson as Julius Caesar with Mr Sunak as one of the assassins.
A string of Conservative MPs – mostly supporters of Mr Sunak – quickly condemned Ms Dorries and branded the attacks on the former chancellor as “dangerous” in the wake of the murder of Sir David Amess.
The Culture Secretary had also previously criticised Mr Sunak for wearing Prada shoes, arguing that such a display of his wealth shows he is out of touch.
Cabinet Office minister Johnny Mercer labelled the “puerile nature” of the leadership contest “embarrassing”.
Greg Clark, the Communities Secretary, warned in an interview with the i newspaper that Labour could exploit the attacks between Ms Truss and Mr Sunak at the next general election.
He urged both candidates to recognise they have “more in common than what divides them”.
Mr Clark’s comments echo those of Conservative former cabinet minister Andrea Leadsom, who also warned in an interview with i that the Tory party could be damaged by personal attacks.
Factionalism and internal strife was apparent long before the leadership election, though.
Partygate and the circumstances in which Mr Johnson felt forced to resign could also mean hostilities and rancour might continue.
Although he is due to leave No 10 in a couple of weeks, the Commons Privileges Committee is set to go ahead with its inquiry into whether the Prime Minister committed a contempt of Parliament by misleading MPs with his partygate denials.
Foreign Office minister Lord Zac Goldsmith wrote on Twitter earlier this month: “The partygate probe is clearly rigged.
“It is a jury comprised of highly partisan, vengeful and vindictive MPs, nearly all of whom are already on the record viciously attacking the person they are judging. It is an obscene abuse of power.”