Leaders' debate: 'Can I vote for the SNP?' voters ask after Nicola Sturgeon's winning performance

Before the leaders’ debate, a panel of voters could not identify Nicola Sturgeon from her picture. The morning, her name was the most Googled term in the whole of the UK.

That astronomical rise was brought about by her much-praised appearance alongside six other party leaders last night.

One poll crowned her the clear winner of the debate with 28 per cent of the vote and while other surveys did not rate the Scottish National Party (SNP) leader quite so highly, she was a constant part of the leading cluster alongside Ed Miliband, David Cameron and Nigel Farage.

If the reaction polls were a reliable indication of voter intention, which they are not, Ms Sturgeon’s party would be getting 20 per cent of the national vote – just one point behind Ukip and another behind joint winners Labour and the Conservatives.

The SNP leader also took the crown in the social media battle, with Twitter analysis showing she was mentioned more than 113,000 times during the live debate and the overwhelming majority of tweets were positive.

By the end of the evening Google data showed that the sixth most searched question was “can I vote for the SNP?” the Guardian reported, and if you put “Nicola Sturgeon” into a Twitter search bar, the words “Prime Minister” will automatically predict.

But voting for the SNP is an impossibility for those living south of the Scottish border as the nationalist party is naturally neglecting to field candidates in England, Wales and Northern Ireland.

Ms Sturgeon, already the Scottish First Minister following Alex Salmond’s resignation, cannot become Prime Minister as the system stands because the SNP’s presence in the House of Commons will never match that attainable by UK-wide parties.

Even if she could, given her party’s position on Scottish independence, running the entire Union is unlikely to be an ambition she holds.

Ms Sturgeon will be hoping that her heightened profile will extend to Scotland, where the SNP has already enjoyed a surge in membership, as it looks towards 7 May and onwards to the Scottish Parliament elections next year.

Her party was certainly happy with last night’s performance, declaring her the winner after initial poll results were published.

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Deputy leader Stewart Hosie said: “Nicola set out the SNP's positive case brilliantly, demonstrating how voting SNP can end Westminster's cuts, and her message clearly has enormous backing north and south of the border.”

Some of her success may have been down to “relaxed” and warm body language, according to expert Robert Phipps.

He likened the Prime Minister to a “headmaster”, said Mr Miliband was “coached too much” and Mr Farage was uncontrolled, “excited and sweating”.

But he found Ms Sturgeon, who clocked up invaluable public speaking experience on Scottish referendum campaign trail, impressive in her controlled manner.

"She was very much like a primary school teacher, bobbing her head up and down, using her hands a lot,” he said.

"She was turning towards the other politicians to listen and challenge them, pointing her fingers and resting one arm on the stand.

"This all tells us she felt quite relaxed and in control."

Additional reporting by PA