The Foreign Secretary won a 34-percentage point lead over Mr Sunak in a YouGov poll of party members, before a survey for the ConservativeHome website put her 32 ahead.
Now in a further blow to the former Chancellor Mr Javid has endorsed the Foreign Secretary and warned “tax cuts now are essential”.
A former chancellor, Mr Javid also warned in an article for the Times that the nation risks “sleepwalking into a big-state, high-tax, low-growth, social democratic model which risks us becoming a middle-income economy by the 2030s”.
He added: “If we can renew our government with a bold agenda, the Conservatives can still beat Labour, the Lib Dems and the SNP at the next election – and the evidence suggests Liz is the best-placed candidate to do so.”
It came as the candidates clashed in the latest Tory hustings in Cardiff, which saw the two answer a series of questions from Tory members.
Ms Truss also once again blamed “the media” for having “misinterpreted” her £8.8 billion policy to cut public-sector pay outside London that she abandoned after criticism from Conservative colleagues.
Asked at the Cardiff hustings about the abandoned proposal, the Foreign Secretary said: “It was misinterpreted.”
Tory tax plans will see £420m budget hole or end of lower tax for most Scots, an…
Pressed by who, she responded “by the media”, despite the plans being in her own press release.
Mr Sunak pounced on the decision, saying he was glad Ms Truss had abandoned the policy.
He said: “I’m glad she u-turned on that policy because I didn’t think it was the right one. It would have meant, I think, potentially almost half a million workers in Wales getting a pay cut, which I don’t think is the right policy to pursue.
“I think you level up by spreading opportunity around, by creating things like freeports, jobs and prosperity by cutting people’s income tax. That’s how I’d like to do it.
“I don’t think cutting the pay of hundreds of thousands of workers here – and indeed across the regions of the United Kingdom – is a Conservative policy that we should adopt and I’m glad that she’s changed her mind.”
The hustings also saw Ms Truss double down on her attacks on the First Minister, after previously labelling her “attention-seeking”.
Turning her attention to the Welsh First Minister Mark Drakeford, she branded him a “low energy version of Jeremy Corbyn” and Sir Keir Starmer as a “plastic patriot”.
Asked if she would “ignore” Mr Drakeford in the same way she said she would ignore Nicola Sturgeon, Ms Truss claimed it was a “very different situation” because the Scottish government is “simply spending their time agitating for independence”.
She added: “The point I was making is a UK Government should be doing what we’re doing which is delivering.
“That’s what we should be doing in Scotland. I think the issue in Wales is different, the problem we’ve got in Wales.”
After a bruising few weeks for the party, Ms Truss also suggested she would want future Tory leadership contests to have fewer debates “rather than airing our dirty linen in public”.
She told a party member: “I do agree with you that there have been some unfortunate occurrences during this leadership contest.
“Some of the things like the debates, I wouldn’t necessarily have so many debates again, I think it’s better if we’re talking to each other within the Conservative Party rather than airing our dirty linen in public.”
It came as the former chancellor announced measures to expand the Prevent programme by widening the definition of “extremism” to include those who “vilify” Britain, with Mr Sunak vowing to focus on “rooting out those who are vocal in their hatred of our country”.
Anne McLaughlin MP, the SNP’s Shadow Justice spokesperson, said: “These dangerous and ill-thought-out proposals from Rishi Sunak are yet another reminder of the depths to which this toxic Tory leadership race has sunk.
“Rather than pandering to right-wing Tory backbenchers and party members, Rishi Sunak and Liz Truss should be more focused on the fact that people across these islands are facing the most horrendous rise in the cost of living most of us have ever seen and it’s under their watch.
“The people of Scotland want no part of the Tories’ race to the right and it’s clear that regardless of who wins the Tory leadership contest, Scotland will lose.”
Former counter-terrorism chief Sir Peter Fahy questioned the precise meaning of “vilification”.
He said: “The widening of Prevent could damage its credibility and reputation. It makes it more about people’s thoughts and opinions.
“It is straying into thought crimes and political opinions.”
Elsewhere, the Scottish Labour leader Anas Sarwar was challenged on if he agreed Ms Sturgeon is an “attention-seeker” who is best ignored.
He said: “I think there’s lots of attention seeking happening in Scottish and UK politics, so I’m not going to criticise anyone for seeking attention because I seek my own attention, as you can imagine, as well – so I’m not going to criticise people for that.
“But what I think is the important point here is I don’t want Nicola Sturgeon to be ignored – I want her to be held to account.”
He said the Tories and SNP were both guilty of throwing red meat to their supporters while the “real issues”, such as NHS waiting lists and the cost of living crisis, are ignored.
Mr Sarwar added: “I want those issues focused on, rather than personality politics between Liz Truss and Nicola Sturgeon, having a fight with each other because it suits them for their own political agenda.”