The first modern election manifesto was issued by the Tory leader Lord Salisbury shortly before the general election of 1900.

Unless his party, he argued, was “armed with a strong majority in the House of Commons”, it would lack the “authority at home and abroad” to deal with a turbulent political era.

There is, as usual, nothing new under the sun. More than a century later and Theresa May’s message is much the same, a strongly personal appeal to “strengthen” her hand in taking on Johnny Foreigner, only she means Eurocrats rather than the Boers or Chinese her predecessor had in mind.

It worked in 1900 (the Unionists got a majority of 130) and, although the Tory lead has narrowed of late, it’ll almost certainly work again. The role, however, of manifestos in election victories is hugely overstated, indeed they’re increasingly out of kilter with modern, TV and online-dominated campaigning.

Last week was awash with coverage of the Labour and Conservative manifestos, picked over by pundits and largely ignored by voters, while today and tomorrow morning we’ll get the Scottish Labour and SNP offerings. Hardly anyone will read them and fewer still will change their voting intention as a result. In other words, it’s little more than an inescapable ritual.

Sure, diehard Corbynistas will try to convince themselves that the Labour manifesto, which isn’t actually all that radical, is responsible for yesterday’s poll showing the Tory lead down to only 9 points, but it probably isn’t. Most voters will have made up their minds long ago as to the relative merits of Jeremy and Mrs May, and little red or blue books aren’t going to change that.

They do, however, serve a purpose in providing the governing classes with cover. A 2015 Tory manifesto commitment, for example, caused difficulties when the Chancellor tried to make changes to self-employed National Insurance contributions, thus why last week’s edition diligently avoided guarantees against rises in NI, income tax and related cuts to pensions.

As the Tory grandee Sir Malcolm Rifkind admitted on BBC Radio 5 yesterday morning, his party’s manifesto couldn’t be full of “glitzy promises” given the likelihood that the next Conservative government “may have to do some things that are not that agreeable and will upset some of our voters”. And when those “things” transpire, the Prime Minister can point to her manifesto and claim a mandate.

No doubt Mrs May would also present this as the sort of “grown-up” politics she claims to epitomise, and it was certainly a dramatic break with Blairite orthodoxy that you don’t go into an election admitting that taxes might go up. But then who expected the Tories to recycle elements of Milibandism from two years ago?

Judging from pre-briefing by Scottish Labour and the SNP over the weekend, such cross-dressing will doubtless continue today and tomorrow. Revealing, for example, that the former chose to trail Kezia Dugdale’s manifesto foreword on opposition to another independence referendum and the demand that the SNP get on with its “day job” – a straight lift from the Scottish Conservatives.

Beyond that, however, Scottish Labour’s pitch is arguably the most intellectually coherent of the campaign so far. While the Tories and SNP obsess over their respective constitutional panaceas, another foreword by Jeremy Corbyn points out that, back in the real world, child poverty in Scotland is increasing, the number of working poor is at its highest level since devolution and health inequalities “stubbornly persist”.

Sure, Brexit is nuts, but the idea that independence and ditching the Barnett Formula constitutes a coherent response is even more so. Now whether the Scottish (or UK) Labour Party has anything genuinely transformative in its manifesto is a moot point, but it’s at least more policy focused than its rivals (the Scottish Liberal Democrat manifesto, to be fair, is yet to appear). Scottish or British nationalism isn’t the answer.

But then intellectual coherence doesn’t a good manifesto make, which is just as well for the SNP is preparing to serve up another triumph of style over substance tomorrow morning. I think I have a copy of every Nationalist prospectus going back to 1997 and while they’ve got glossier with each election, this has been at the expense of anything approaching a coherent political philosophy. Who could forget the “cult of Nicola” launch prior to last year’s Holyrood election?

Alex Salmond and Nicola Sturgeon spent last week complaining that Jeremy Corbyn had pinched lots of SNP policies for his UK manifesto, but they should know all about that. At the 2015 general election, when the SNP inexplicably unveiled “Stronger for Scotland” at a rock-climbing centre, it practically lifted whole paragraphs of policy from a Scottish Labour Party it had spent years deriding as “red Tory” and irrelevant.

The leitmotif of this opportunistic approach is the 50p tax rate, once again being wielded as the “centrepiece” of the SNP manifesto, despite having been so two years ago and then jettisoned as soon as the Scottish Government actually got the power to put it into effect. The First Minister gets around this particular contortion by pretending her party will be able to implement it across the UK rather than just, you know, the bit of the UK she actually governs.

That, and one suspects the manifesto more generally, will reinforce the impression that the SNP has simply exhausted its once formidable campaigning machine, thus its retro 1987-like narrative predicated on all the usual Tory bogeymen and women. We’re told tomorrow’s offering will do three impossible things before breakfast: “protect” Scotland from Tory cuts, build a fairer society and strengthen Scotland’s “hand” in the upcoming Brexit negotiations.

Well, I suppose they had to put something in the manifesto, and this is something, so there we will be. Independence or a second referendum, meanwhile, looks likely to have been relegated to a perfunctory paragraph or two. It’s almost as if that March press conference at Bute House never happened; the expected fillip hasn’t appeared, and even the prospect of “perpetual” Tory rule probably won’t alter that reality.

Meanwhile, we must endure another few days of manifesto tedium. With so many elections over the past few years, they’re fast becoming like Democratic and Republican “platforms” in the United States, unread, unloved and peripheral to electoral success or failure.