Is this the 'most dangerous woman in Britain'?

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Nicola Sturgeon, has risen up the ranks of U.K. politics from bit-part to the role of "kingmaker" in the next British government.

But how can the first minister of Scotland and leader of the Scottish National Party (SNP) decide who could be the next U.K. prime minister?

With less than two weeks to go before the U.K.'s general election on May 7, CNBC has the lowdown on who Nicola Sturgeon is and why we should care.


Who is Nicola Sturgeon?

Sturgeon, who joined the SNP at the tender age of 16, has overseen a sharp rise in popularity for the nationalist party.

She became the pro-independence party's leader in 2014 after the SNP failed to persuade Scots to vote for an end to a 300 year-old union between Scotland and the rest of the U.K. The SNP's then-leader, Alex Salmond, resigned following the party's defeat making an emotional resignation speech in which he said: "For me as leader my time is nearly over but for Scotland the campaign continues and the dream shall never die."

The job of carrying the torch for independence fell to Sturgeon who was the only nomination in the leadership race and the only woman ever to hold either position as leader of the party, or of Scotland.

What's she like?

How UK election works
How UK election works   

In spite of the 2014 defeat, the SNP's membership has since increased to reach more than 100,000 people by this March, making it the third-largest party in the U.K.. The increase in popularity has largely been attributed to Sturgeon's leadership style.

Not only has the SNP's manifesto and election campaigning been covered in detail, Sturgeon has also taken part in several televised debates in which she was declared the winner.

Sturgeon certainly appears to be enjoying the limelight, saying that the Daily Mail newspaper's remark that she was "the most dangerous woman in Britain" was "possibly one of the nicest things the Mail has ever said about me."

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With her easy public manner and persuasive debating techniques, political leaders in London have become worried about Sturgeon's influence and her manifesto pledge to "shake up the out-of-touch Westminster system so that it serves Scotland better."

That pledge, along with its main manifesto promises to end austerity measures and increase health spending, as well as blocking the renewal of Britain's nuclear deterrent (which is based in Scotland) and maintaining its support for independence, are proving popular with Scottish voters, at least.

The latest poll by Panelbase of 1,044 voters in Scotland between April 20 and April 23 suggest the SNP could see the number of MPs it has in the British parliament rise from six to 53 with the latest polls suggesting that 48 percent of voters support the party.

Since Scotland entered a political union with England in 1707, it has sent representatives to London's parliament, and Scotland currently has 59 parliamentary seats (with each seat representing a constituency). Polls suggest that the SNP could take almost all of these seats, giving it significant representation in the Houses of Parliament.

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The Scottish parliament, by contrast, is made up of 129 Members of the Scottish Parliament (MSPs). It has powers to make laws in Scotland, except on certain matters.

In contrast, support for the Labour party in Scotland has fallen while the Conservatives, a party that has never done well among the predominantly working-class voter base in Scotland, are expected to not win a single seat in the country.

On the party's website it states that a vote for the SNP would allow the party to use its "influence at Westminster to help deliver positive change for the benefit of ordinary people, not just in Scotland, but across the U.K."

Kingmakers

If the SNP does gain as much of the vote in Scotland as expected, Nicola Sturgeon could become a "kingmaker." If there is no outright winner in the May election, Sturgeon will have a very big say in who makes up a minority or coalition government.

The SNP states on its website that it will "never put the Tories into power" and has appeared to edge closer to Labour – a leftwing party whose policies are more akin to the SNP's.

"If there is an anti-Tory majority after the election, we will offer to work with other parties to keep the Tories out. And we will then use our influence to demand that Labour delivers the real change that people want and need - instead of just being a carbon copy of the Tories."

While the SNP's call to arms might be popular with Scottish voters, the message is not going down so well south of the border.

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Aware that the majority of English voters do not like the thought of SNP influence over English law-making and governance, the Labour party appears to be distancing itself from the SNP – particularly as the Tories try to make hay out of the potential alliance as a scare tactic, telling voters a SNP-Labour coalition would mean "chaos."

In a bid to reassure voters than a vote for Labour would not shoe-in an SNP coalition by the back door, Labour leader Ed Miliband told the BBC's Andrew Marr show Sunday that there would be no deals, saying "I want to be clear about this: No coalitions, no tie-ins...no deals."

Confident about the SNP's performance on May 7, Nicola Sturgeon replied to the remarks by saying Miliband would have to "change his tune" after the election.

- By CNBC's Holly Ellyatt, follow her on Twitter @HollyEllyatt.