For those who believe in the survival of the union between England and Scotland, these are obviously febrile, fragile times. The latter country’s experience of the independence referendum has sent the SNP’s poll ratings soaring, and the prospect of the country underlining its political distance from England by sending a huge bloc of that party’s MPs to Westminster now looks inevitable.

Over the weekend, the Tory grandee Kenneth Baker floated the somewhat unlikely idea of a grand coalition between the two big English parties to avert a constitutional crisis; a few days before, my Guardian colleague Martin Kettle wrote a somewhat more level-headed column expressing doubts that “either of the men about to contest the premiership know … they too have a country to save and rebuild”.

From a unionist perspective, they certainly do – so now may not be the best time to be fanning tensions between England and Scotland, nor telling Scottish people that no matter how many of them vote for the SNP, the nationalists should never have a sniff of influence and power at Westminster. Yet that is exactly what David Cameron is doing, with apparently no concern for the consequences.

There have already been those Tory posters featuring Ed Miliband and Alex Salmond – and, on later versions, Gerry Adams – suggesting that an SNP-Labour government would be beyond (English) voters’ “worst nightmare” and spell “chaos for Britain”. On Saturday, just to hammer the point home, the prime minister demanded that Miliband rule out any deal with the SNP, so as to prove that he “cares about this country”. And today, there comes news of a new Tory poster depicting Miliband peering out of Salmond’s pocket. The Tory chairman, Grant Shapps, has already been on Twitter, bigging up this new wheeze in truly Churchillian terms: “NIGHTMARE! Ed Miliband as PM, propped up by Alex Salmond ‘calling the tune’ if Labour gets into Downing Street.”

For a party that habitually thunders on about the catastrophic idea of Scotland exiting the UK, this is pretty remarkable behaviour. Few so far have pointed this out, but it bumps up against some particularly interesting facets of recent Conservative history: the fact that in the Scottish parliament of 2007-11, the Scottish Conservative party regularly supported the supposedly awful, evil SNP; or that late last year, the Tory leader in Scotland, Ruth Davidson, refused to rule out an SNP/Conservative deal at Westminster.

It also underlines the fact that a Tory prime minister who once encouraged us to believe that he was a centrist, One Nation kind of Conservative now seems dangerously close to granting the wishes of a very different part of the Tory family: that rather mad-eyed, fundamentalist tribe, usually associated with the English south-east, who would blithely wave goodbye to Scotland in the service of what they assume would then be permanent Conservative government.

In that context, consider Cameron’s recent record. Quite apart from his questionable handling of the referendum itself, responding to the no side winning (a term to be used advisedly) by bundling up a guarantee of increased powers for Holyrood with what the Tories call English votes for English laws looked provocative, cynical and crassly neglectful of the delicate state of Scottish politics. As Alistair Darling warned him, it played straight into the SNP’s hands.

It’s certainly an interesting look: a fast-and-loose approach to the very existence of the UK

From a broader perspective, the fact that the Conservatives are going into the election on a prospectus guaranteed to further alienate the majority of Scots – even crueller cuts, the prospect of Britain leaving the EU after a referendum – is of a piece. And now comes this latest twist in the Tory election campaign: decisive proof that the Tory view of Scotland is of a strange land of political ghouls and monsters to be mostly ignored, but occasionally used to scare the English.

Listen to the inestimable (and very quotable) Scots Spectator writer Alex Massie, whose critique of the original Miliband/Salmond poster applies just as much to this latest version – and, in fact, what looks increasingly like the Tory approach to the Scottish element of this election writ large.

“It frames the election as a battle between Scotland and England in which the latter is menaced by the former,” he wrote in January. “It pits the two largest parts of the union against one another. Which, of course, is exactly how the SNP likes it; precisely how the SNP sees the election – and the future of Britain – too.

“The Scottish Nationalists will not mind the Tories stoking the fires of English nationalism. By ‘not mind’, I mean, of course, that they will be delighted. Yet again, a notionally unionist party is helping the nationalists achieve their ambitions.”

Are Scottish Tories – Michael Gove, Liam Fox, Lords Forsyth and Strathclyde, even poor old Malcolm Rifkind – not at least a little nervous about all this? For Conservatives, it’s certainly an interesting look: a fast-and-loose approach to the very existence of the UK that gives the lie to what was once their biggest article of faith.

The union jack adorns Tory campaign bumf just as much as ever. But what kind of British patriots are these, exactly?