Since Nicola Sturgeon took over as leader of the Scottish National Party from Alex Salmond in 2014, after the ill-fated independence referendum, she has cemented her status as his rightful heir with her confident performances and principled politics.

And through the leaders debates, in which she attacked Labour leader Ed Miliband from the left on issues such as austerity and the Trident nuclear deterrent, she has reached a UK-wide audience, winning sympathy in England and Wales despite her nationalist Scottish politics.

Parts of the left despair at the centre-minded political pragmatism of the Labour party who, after the reform of the Blair years, understood that power and effectiveness meant compromising on long-held beliefs.

Untainted by the realities and complexities of Westminster power, Sturgeon sticks rigidly to her left-wing principles. To many, this is refreshing. Sick and bored of pragmatic centrism, they want the surefootedness of principle politics, no matter the cost. Clear dividing lines make the choices easier for voters, like in the days of Thatcher versus Foot.

But Sturgeon's critics accused her of demagoguery. That her principles are naive populism and she is over-promising because she knows she will not be shackled by the realities of having to form and sustain a Westminster government. She will never be the protagonist in a Downing Street drama, just a member of the supporting cast.

Sturgeon may well prop up a minority Labour government in Westminster with some sort of deal, depending on the outcome on 7 May. Projections suggest the SNP will more or less wipe out Labour MPs in Scotland. Her manifesto was trailed as a pitch to the whole of the UK, not just voters north of the border, perhaps to soften up the idea of SNP-as-kingmaker in Westminster.

The Conservative party is warning that it will mean Miliband having to kowtow to SNP whims and wants so it can secure power, at the expense of the UK as a whole. But many English and Welsh left-wingers welcome the prospect of SNP influence in Westminster.

So the question is this: Is Nicola Sturgeon a force for good in UK politics? Vote in our poll.