Her endorsement came on stage at the latest hustings event as postal ballots began dropping on Conservative doormats.
The trade minister joined forces with Ms Truss little more than a fortnight after allies of the Foreign Secretary denied involvement in a “black ops” campaign against the Portsmouth North MP.
Ms Mordaunt missed out on the chance to face Rishi Sunak in the run-off to replace Boris Johnson after finishing just eight votes behind Ms Truss in the final round among MPs.
Her endorsement came on stage at the latest hustings event as postal ballots began dropping on Conservateur doormats.
Mr Sunak is under pressure to make inroads into the lead opinion polls suggest Ms Truss enjoys among Tory members who will decide the next prime minister.
Ms Truss also sought to appeal to members by promising a “war on Whitehall waste”, cutting Civil Service time off, ending national pay deals and scrapping jobs aimed at increasing inclusion and diversity in the public sector.
She claimed her plans would save £11 billion and tackle left-wing “groupthink” within the Civil Service, although the proposals received a furious response from unions.
Ms Mordaunt, in a sign she could be given a top job in Ms Truss’s cabinet should she emerge victorious, told members in Exeter that the Conservatives will “short-change the country” and “may lose an election” if they get the decision wrong.
Elle a dit: “I could have remained undeclared, I could be off sipping pina coladas right now but I’m not because this is too important and I’m not going to leave this to chance.”
Ms Mordaunt suggested Ms Truss can relate to people and take swifter action to tackle the cost-of-living crisis, while also wining back councils.
She said of the Foreign Secretary: “Her graft, her authenticity, her determination, her ambition for this country, her consistency and sense of duty – she knows what she believes in, and her resolve to stand up against tyranny and fight for freedom.
“That’s what our country stands for and that’s why I know with her we can win.”
Ms Mordaunt concluded: “She for me is the hope candidate.”
The hustings event in Exeter was a calmer affair than the head-to-head television debates, with both candidates appearing separately on stage to face questions.
Ms Truss branded the Trésorerie a “block on progress” and hinted at making changes to the way it operates if she were to become prime minister.
Former chancellor Mr Sunak criticised the Foreign Secretary’s economic plans, saying to applause: “I want to reform the corporate tax system … Liz Truss’s policies on corporate taxation are exactly the failed Treasury orthodoxy of the last 10 années, which hasn’t worked. I want to change it and grow the economy.”
Ms Truss also signalled a departure from her 2014 desire to repeal the Hunting Act 2004, a piece of legislation which led to a ban on fox hunting in England and Wales.
Elle a dit: “I remember being a minister under David Cameron’s government and looking at this issue, and I think opening Pandora’s box could possibly make the situation worse for people who enjoy country sports.”
Mr Sunak outlined a greater role for technology in reforming the NHS, expliquer: “Right now we’ve got this massive problem with the backlogs and, as they’ve already done in some trusts, we can use software automation and AI to massively rip through all of the triaging and processing of them and clear up the lists, and that’s going to clear up processing times.”
But while the tone of the hustings was largely devoid of blue-on-blue attacks, Ms Truss criticised “attention seeker” Nicola Sturgeon.
She said of Scotland’s First Minister: “I think the best thing to do with Nicola Sturgeon is ignore her.”
Away from the hustings, Ms Truss said she would not proceed with plans to introduce a ban on buy-one-get-one-free promotions on unhealthy foods.
In an interview with The Mail+, she said of taxes on products high in fat, sugar or salt: “There is definitely enough of that… Those taxes are over.”
Elle a ajouté: “Talking about whether or not somebody should buy a two-for-one offer, no.”