Below, our writers offer their verdicts on what happened - and who came out on top:
Iain Dale: Sunak was so dominant it often came across as mansplaining
Sometimes the person who wants something the most is the person who prevails.
Rishi Sunak came out of the traps firing on all cylinders, barely allowing Liz Truss to get in a word edgeways in the discussion on inflation and growth. Unfortunately, he was so dominant it often came across as domineering mansplaining.
The trouble is, Ms Truss had few believable answers. Cut a tax here, cut a tax there; borrow a bit more here, don’t pay any of it back for three years. This is the antithesis of "sound money" Thatchernomics, a point Sunak drove home well.
Truss then called Faisel Islam 'Fayzell' twice, before falling into Sunak’s trap of using the phrase "Project Fear", allowing him to point out that it was she in the Brexit referendum who was part of "Project Fear".
Her rather limp reply of "perhaps I have learned from that", was just that – limp. However, she did improve.
But Sunak was on fire. No one watching this debate could surely come to any other conclusion that Sunak would be the better prime minister.
There are many questions Tory members need to ask themselves, but can any of them truly believe that Truss is more likely to win an election than Sunak? If they do think that, their powers of self-delusion are far greater than mine.
Juliet Samuel: I find it hard to trust Sunak at all
Oh he’s so clever, isn’t he? And yet, it’s not charming. In fact, it’s a bit annoying, and in some cases, downright slimy.
There were moments early in Monday night's debate when Sunak had Truss on the ropes. The problem was that far from showing her up with his talk of interest rates that would "tip millions of people into misery", Sunak was trying very hard not to smile. He talked, she tried to talk; she stumbled, he tried not to smirk.
The economic debate was vigorous and neither side won conclusively. But it was on China that his attacks were harder to take. We ought to remember that Sunak is the man who pushed hell-for-leather to reopen trade talks with China at a time when Beijing had stuck his own fellow Conservative MPs on a sanctions list for daring to care about freedom in Hong Kong. It was Sunak’s treasury that watered down language on China in Britain’s major review of national security last year.
And yet, he had the gall to claim that Truss, the Cabinet’s foremost Beijing hawk, had "been on a journey" on China, just like him. I’m not sure I trust Truss’ judgement, but I find it hard to trust Sunak at all.
Tom Harris: Sunak’s aggressive challenges risked falling flat
Would Sunak have been quite as vociferous, quite as aggressive, or talked quite so fast, had opinion polls of Conservative members not placed him more than 20 points behind his rival?
The debate at first threatened to be a serious affair, with measured, respectful exchanges. But it quickly degenerated into a tense, bad-tempered argument, and the responsibility was largely Sunak’s.
It was the former chancellor whose impatience, and perhaps his fear of losing, shaped the tempo of the debate, so keen was he to achieve a "gotcha" moment that would expose his rival’s lack of economic experience and knowledge.
So it must have been frustrating for him that despite his repeated interventions – perhaps because of them – it was Truss who emerged with the better sound bites, if not better arguments.
The Foreign Secretary understands her intended audience in this campaign and her economic platform – essentially postponing the dreaded day when we will have to start paying back the Covid debt – is aimed at those who want to believe that tax cuts sooner rather than later are advisable, not just attractive.
Sunak’s arguments may have been correct, but his aggressive challenges risked falling flat.
Liam Halligan: Sunak’s frantic interruptions did him no favours
A week ago, Truss and Sunak collectively refused to take part in a three-way debate with Penny Mordaunt. With an opponent they both feared dispensed with, the two prime ministerial hopefuls returned to the televisual arena.
From the outset, the focus was on the economy – and with household energy bills heading for £3,000 per year this autumn, Sunak was unable to confirm he would deliver more help to cash-strapped households.
Truss countered with specifics – pledging to reverse the April national insurance rise while suspending green levies on electricity bills and freezing the former chancellor’s upcoming rise in corporation tax. "No other country is putting taxes up at the moment," she said. "The UK is an outlier."
Sunak, supremely well briefly and armed with damning quotations from his opponent, was combative throughout. "We need to get a grip on inflation – what Liz is advocating would lead to more price rises, costing everyone more in the long run," he said.
As the debate slowed, they started joshing over the former chancellor’s fashion sense, while downplaying the negative briefings doled out by their respective spin operations.
But Sunak’s repeated, sometimes frantic interruptions had done him no favours. For once, Truss’s slow, methodical approach – for which she’s been criticised in the past – helped her gain the upper hand.
Patrick O’Flynn: Sunak will barely have scraped a draw in Tory members' eyes
Sunak went into this debate so far behind that some of his more prudent allies might well have thought his best bet was to keep things collegiate with Truss and plan his future on the basis of coming a respectable runner-up.
Being seen as the prime instigator of the successful plot to bring down Boris Johnson and the main roadblock to tax cuts are formidable disadvantages in the eyes of the Tory faithful.
Being outed as one of the Cabinet ministers who sought to thwart Truss over her hard-line strategy to force Brussels to give ground on the Northern Ireland Protocol was another nail in the coffin of his leadership hopes, while his lack of ministerial experience outside the Treasury has deprived him of depth and breadth as a serious political thinker.
Yet Sunak did not sue for peace and a plumb portfolio in a Truss Cabinet. Instead, he went for the jugular – attempting to deliver a knockout blow and showing her scant respect by frequently interrupting and talking over her.
Her economic plans were "not moral and…not Conservative", he argued, summoning the spectre of sky-high interest rates and crippling debts that would follow the "short-term sugar rush of unfunded tax cuts".
His onslaught didn’t really work because Truss held herself together throughout, jabbing back effectively about the lack of a growth plan for the economy. Looking the part in a sleek blue dress certainly helped. But so did a certain steeliness of character that communicated itself throughout.
When Sunak claimed to want to stand up to China, she magisterially commented: "This is not something you advocated in government, I’m delighted you have come round to my way of thinking." Shades of Maggie Thatcher there. Her loyalist defence of Boris Johnson late in the debate will also have won her credit among the Tory faithful.
Overall, the slick Sunak probably won on points in the eyes of the general TV audience. But in the eyes of Conservative members he will barely have scraped a draw.
On the basis of this debate, despite him stating his readiness to serve in a Truss administration, he will actually lurk on the backbenches waiting for her to fail and expecting her to as well.