So this 20-year-old’s first speech in Westminster has been getting a lot of social and traditional mainstream media attention. Which few speeches that don’t have direct policy import (Budget, Queen’s Speech, that sort of thing) do. If you know me, you know my first response (well before, say, watching the videos) is to ask why.

It might be because she’s Britain’s youngest ever woman MP, and youngest MP regardless of gender for centuries. But I doubt that’s most of it. Dare I say if she looked a little more like Louise Mensch this might be a bigger factor.

It’s probably quite largely because of the straight-talking rhetoric, significantly different to the normal buzzword selection of Westminster rabble-rousing. The line about being the only 20-year-old in the country the Chancellor is interested in helping to house is already working its way into political history.

But I think there are two other, intertwined factors: party affiliation and content.

The SNP have provided some much-needed lightening of the Westminster tone since suddenly going from a barely present huddle of MPs to the third largest group in Parliament – taking gleeful selfies in the chamber, refusing to abide by various forms of traditional but uncodified behaviour, etc. But this shouldn’t distract observers from their real importance – and neither should the issue after which they are named, seeing that there is clearly more to the phenomenon than that.

The recent rise of the Scottish National Party has been little less than meteoric. That remains the case despite the No vote in the independence referendum and despite not ending up as Westminster kingmakers. A reminder: in a proportional representation Scottish Parliament, they managed to survive a full term as a minority government (with the UK-wide parties generally minded to oppose a lot of their policies), and then get elected to an absolute majority off the back of it. Single-party absolute majorities are notoriously rare in PR systems. Their membership is something like five times what it was three years ago – a rise that has taken place mostly immediately after the referendum defeat that many assumed (and I tended to be one) might kill the party altogether, or at least divide it too permanently to be a significant political force for decades. And they now hold 56 out of 59 Scottish Westminster seats, sitting between the really big two well into triple figures, and everyone else including the Lib Dems with eight MPs or less.

There is therefore a governing record to look at as well as a rhetorical one. And while the SNP performance in Holyrood government is certainly not perfect, it is presumably the driving force behind a fair bit of their election success since their first governing term. It can be summed up quite easily: genuine left-wing. They have abolished prescription charges, kept university fee-free, and generally pursued a big-state, high-tax high-spend, socialist-liberal governing agenda wherever they have had control and Scottish independence has not been at issue.

In this context, Black’s attack on cuts to housing benefit is true to party line. But it’s also true to a lot of thinking grassroots frustration across the UK, and I think this is the other large part of its appeal.

Westminster, at least until the de facto arrival of the SNP, has been getting heavily stuck in a centre-right consensus that increasingly seems more right than centre. Voices questioning the efficacy of austerity as a response to recession have been condemned to the lunatic fringe. The Labour party has responded to the increasing success of the increasingly far right by moving to the right in the belief that the voters are there, rather than to the left in a bid to offer a genuine alternative. Cameron has somehow managed to pass off policies and actions which are often by any objective measure more extreme than anything carried out by the infamous Thatcher as managerial, sensible safe-pair-of-hands decisions.

Frustration at General Election polling is nothing new. But the problem of what to vote with a left-leaning set of ideas was particularly acute. The Lib Dems, after a term as junior coalition partner, looked not very liberal, somewhat questionably democratic and decidedly a spent political force. Labour were so little the labour party that they were trying to resist the label ‘Red’ applied to their own leader – how did no one in the political classes comment on the idiocy of this?! Quite a lot of Green votes (including my own) were cast in seats where the candidate had no real prospect of winning – and probably more would have been if there was no likelihood of thereby helping a Tory or even UKIP candidate into parliament.

The Scots, of course, if they felt this way, had a solution. They voted SNP (along with, seemingly, most of the rest of Scotland).

The SNP, particularly during and since the referendum campaign, have emphasised the degree to which they are out of step with the Westminster-based parties, playing themselves up as a real alternative. It’s a PR ploy of course, but it does represent some reality of policies beyond the independence question too.

Most of the people I’m in contact with through social media and the web are of course broadly like myself – middle-class-ish liberal lefties, quite possibly neo-hippies, quite a lot Christian (of a not very evangelical persuasion generally), and very few Scots. They don’t represent the country. But they do represent a certain demographic. And I think the core of the reason I encounter the video of Mhairi Black’s maiden speech several times a day is that amidst Greece providing a worked example of austerity not working and the Labour interim leader advocating non-resistance to various welfare cuts, it represents a line of thought, opinion, values, belief and, actually, evidence-based reasoning much closer to their own than almost anything else being said in Parliament (honourable exception for Caroline Lucas).

I would vote No in a Scottish independence referendum without hesitation. But I’d happily vote SNP in a government election.