PITY the poor Edinburgh festival entertainer. There they are, piling up debts to put on a show in the hope of stardom, only to find themselves in competition not just with every Tom, Dick and Harriet who ever flitted across an Oxbridge stage, but with the biggest, hammiest luvvies of all: politicians.

Nicola Sturgeon started the ball rolling with a sit down with LBC’s Iain Dale, followed by the Scottish Conservatives leader, Ruth Davidson, in conversation with another host. Both chats took turns for the personal, dwelling on children, having or not having them, in ways that they probably would not if the interviewee had been a man. One step forward for the caring, sharing society, two steps back for feminism: discuss.

John McDonnell, the Shadow Chancellor, had his own show-stopping routine. He told Dale that if the Scottish Parliament voted to have a second independence referendum then a Labour Government in charge of an “English parliament” would not block it. Other views were available, he added.

Too right they are. In its manifesto for the 2017 General Election the party said it would not support indyref2. The Scottish Labour leader Richard Leonard, on the rare occasions he surfaces to give an interview, has repeated the assertion. The UK leader, Jeremy Corbyn, has done a Brexit on the matter, saying he will make up his mind if and when a request was made. Opposing another referendum is not a whim, it is a central pillar of Scottish Labour’s pitch to the people, one that Mr McDonnell smashed with a wrecking ball.

Whether he acted initially from ignorance, carelessness, or both, he doubled down on his position yesterday, leaving the party in Scotland looking even weaker and more irrelevant. This is worse than being treated like a branch office. Scottish Labour now looks like the unpaid intern to Labour in London, hanging around waiting for a chance to make the tea.

READ MORE: McDonnell ignores Leonard

There is another explanation for his less than soft shoe shuffle into Scottish political territory. He is not the only one trying to make new friends ahead of the great September showdown in the Commons. While Mr McDonnell was speaking in Edinburgh, the First Minister was in Glasgow telling an audience that “some kind of progressive alliance” between the SNP and Labour to lock the Tories out of Government would not be the worst idea that she had ever heard.

The Scottish Tories have been gleeful, seeing this as a chance to haul out those old posters of Ed Miliband in the pocket of Alex Salmond and get busy Photoshopping. That any deal would be received badly in south of the border was clear from the headline in the English edition of the Daily Mail, which went for “Labour gets into bed with the SNP”, while the Scottish edition plumped for “I’d help Corbyn get keys to No 10, admits Sturgeon”.

Though Labour has said repeatedly that it is not interested in any governing pacts, it would of course say that, wouldn’t it. But in the bizarro political universe that is contemporary Westminster, the notion that the SNP would prop up a Labour Government might work to the advantage of Jeremy Corbyn. Ms Sturgeon, as is known from past elections, is well regarded outside Scotland. Remember those tweets and letters after the TV debates from people wishing they could vote for her? Far more experienced in government than any of the Labour front bench, she could be seen as a steadying hand.

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From Ms Sturgeon’s side, a deal with Labour would be a certain path to another independence referendum, particularly tempting in the wake of the Ashcroft poll showing 52:48 in favour of Yes, if not to her then to many in the party’s increasingly impatient ranks.

But who are we kidding here? A Labour SNP alliance, pact, temporary bunk up, call it what you will, is a terrible idea. How bad? Fireworks display in a phone box bad. Cat marries canary bad. Clackers bad. So bad that even Ms Sturgeon is trying to get out of any arrangement before it has even begun, hence her additional talk on Tuesday of being “no great fan of Jeremy Corbyn” and insisting he take “a very firm anti-Brexit position” as a precondition of any alliance. Good luck with that. She might as well have asked him to vote Tory.

Any SNP-Labour alliance would destroy the Labour Party in Scotland. While that might seem to opponents to be merely hastening a process already underway, or even just punishment for past misdemeanours and arrogance, they should be careful what they wish for. As many a non-Brexit related issue shows, whether it be in the building of a children’s hospital or exam results, the last thing this Scottish Government, any Scottish Government, needs is less scrutiny.

Having a Scottish party propping up a UK government also takes us into choppy constitutional waters. It is clear after the votes on abortion and same sex marriage in Northern Ireland that the SNP takes a more casual approach to voting on devolved matters than previously stated. Even so, how soon would it be before a Labour Government asked for help above and beyond supply and confidence, say? Having bent its own principles once, would the SNP be tempted to be flexible again? Looking at it from another direction, would the SNP really vote down a Labour Government?

Not for the first time, politicians, in Scotland and further afield, need to acquire a sense of perspective, fast, as the Brexit deadline looms. The sense of disillusionment among the electorate with politics and its practitioners is palpable. To watch Mr McDonnell and Ms Sturgeon engage in megaphone diplomacy with each other is hardly dignified and may ultimately prove to be premature and unwise.

READ MORE: Labour accused of betrayal

With no hope of cool heads in Downing Street as a no deal Brexit looms, it is up to others to make the best of a possibly calamitous situation. Labour and the SNP have parts to play in that, but so do other individuals and parties. To put it in terms Mr McDonnell may recognise, this is about the future of the many, not the few.