The moment the Conservatives were waiting for in the Challengers debate for Opposition leaders came right at the end.

Until then, David Cameron may have been regretting not being at the debate to answer the attacks on the record of his party in government. Until then, Ed Miliband had been able to look Prime Ministerial, merely by resisting the demands of the other opposition leaders for an end to austerity, calmly reminding them that they weren’t the ones who would be responsible for actually keeping the books in balance, however many MPs they had. Until then, Nigel Farage had been given a free rein to represent not just the right, but the centre too, positioning UKIP as the true home for low taxes, investment in defence and controls on immigration. I could almost imagine Cameron sitting at home, glass of Dom Perignon at his side, becoming increasingly forlorn as the realisation hit him that this might be a missed opportunity and causing more damage to the Conservatives that it was avoiding by him not being there.

Then it happened.

Answering a question about the conditions that they would want to enter into a coalition with each other, Nicola Sturgeon, the Leader of SNP, who once again performed superbly, made a clear advance to Ed Miliband, offering to support him and the Labour Party in number 10. Miliband attempted to bat this away, saying that he couldn’t enter into a coalition with a party that wants to leave the United Kingdom. but Sturgeon wasn’t having any of it. Pointing out that the question of Scottish Independence was not relevant to this debate, and in fact this election, Sturgeon said that Miliband should be concentrating on finding issues on which they agree. Miliband tried again to resist, pointing out that the two parties had profound differences. Sturgeon was ready for this too, emphasising that all of their differences pale into insignificance compared to their shared wish to get David Cameron out of Downing Street.

Then Sturgeon laid out her conditions. She and the SNP would be prepared to support Labour in Downing Street not just on the basis of them being there, but if they can offer “replace the Tories with something better”. Having spent most of the debate taunting Miliband as a ‘Tory-lite’ lover of austerity, Sturgeon said that the strings she would attach to supporting Labour would be for them to cut less and spend more.

That was the moment when Cameron and his wife Sam must have clinked together their champagne flutes in satisfaction, as, in front of the whole country, and in particularly the press, Sturgeon had clearly emphasised that whatever Labour were saying in their manifesto about budget responsibility, if they actually wanted the votes to get anything done in Parliament, that would have to go out the window. We also saw a further sign of the formidability of Nicola Sturgeon’s negotiation and debating skills, which is why it took little time for the Tories to re-publish their photo of Sturgeon with Miliband in her pocket. The Conservatives wanted a reminder that not voting for them would be a vote for chaos as Labour cannot get a majority and will rely on the SNP. They got one.

Other notable moments from the debate included a much stronger performance from Nathalie Bennett, the Green Party leader, who had either been practising or had finally had some public speaking training. She made a strong defence of her Britishness, having come here from Australia, and attached Ed Miliband hard by using Rachel Reeves’s comments on Labour not being the party of people on benefits well, albeit out of context. Nigel Farage chose to train his sights on the BBC audience, claiming that they were typically left-wing, drawing a rebuke from moderator David Dimbleby, who assured him they had been fairly chosen, at which point Farage looked at the camera and said “well the audience that matters is at home.” He knows what he is doing, does Nigel, and whilst the other leaders went into the audience to shake hands at the end, he walked straight off, an outsider, just as he would like to be seen. I would like to come up with a notable moment from Leanne Wood, but this time there was very little, apart from being some sort of anti-austerity outrider for Sturgeon.

Someonthing else that was notable was what was missing. Perhaps no surprise with phalanx of mostly left wing political leaders. Not a single mention of wealth creation and enterprise. The whole night. Not one. Plenty of taxes and public spending though.

The winner inside the studio was Nicola Sturgeon. The winner overall, as the debate descended into a sort of left-wing chaos, was David Cameron. But he had to wait for Sturgon to help him win.