BORIS Johnson will swat away the SNP like midges, according to Scottish Tory MPs. Well, he may be about to find that it's extremely difficult to swat away midges. As any hillwalker knows, the little devils tend to cloud around your head, and no amount of swatting gets rid of them. The only escape is to run to the car and spray madly.

Mr Johnson has been doing a pretty good job of swatting himself recently and his interviews are becoming a serial calamity. But he is still heading for victory in the Tory leadership. It's time to consider just what happens on the 25th of July, a day that is likely to live in infamy.

Up to a dozen Tory MPs, including Kenneth Clarke, have resolved to vote against any Boris Johnson administration in a confidence motion – that's if Labour gets a chance to table one before the summer holidays (holidays you say – at a time like this?). But even if it is postponed till September, the numbers look very bad for Mr Johnson.

READ MORE: Ruth Davidson could be in Brexit negotiating team 

The Tories have an ever-shrinking majority of three even with the help of the DUP. It's quite possible that Boris Johnson's premiership could be a one-day affair. But what happens then? Well, if the leader of the majority party is unable to win support of the house, after two weeks, Jeremy Corbyn has a chance to try his luck. But he is even less likely to win a Commons majority right now.

The Queen can't help since she is just a figurehead. It would be for the Speaker, John Bercow, to remind parliament that the only alternative is a general election. MPs will slouch back to their constituencies preparing for a horrendous time from angry voters who are fed up with the lot of them.

HeraldScotland:

Both the Tories and Labour realise they are in for a drubbing. The Tories: for failing to deliver Brexit and for wasting three years. Labour: for being hopelessly divided over Brexit and for having a leader who's turned equivocation into a fine art. Even if Labour does a back-flip, and supports a People's Vote, it may be too late. This would alienate many Leave voters in Labour's 40 target seats.

The people cheering loudest will be the Brexit Party, followed by the SNP and the Lib Dems. On the basis of the EU referendum showing, the Brexit Party stand to win the next general election, but that's not going to happen. Results in Euro elections rarely translate into seats in the Commons.

READ MORE: Boris Johnson will 'swat' SNP like midges, claim Scottish MPs 

But Nigel Farage's people must be in the running to get 60 or 70 seats. The SNP are in line to get 50 seats, and the Liberal Democrats around 30, along with 10 DUP and a handful of Greens and independents. If the Tories return, say, 240 MPs, and Labour around 250, the arithmetic becomes excruciating.

Labour would claim victory as the largest party. But the Tories would claim to be larger if you include the DUP and the Brexit Party (assuming Nigel Farage agrees). Labour would respond that if you add in the Liberal Democrats, and the SNP, none of whom would support a Conservative Prime Minister, then Number Ten is there for Jeremy Corbyn's taking.

But then the midges would appear in force. Nicola Sturgeon would surely demand a referendum on independence for Scotland as a precondition for entering any confidence and supply coalition with Labour. “Confidence and supply” means that they back Corbyn as Prime Minister, but don't agree to support all his policies. This would be a horrendous situation for the Labour leader.

His party is already deeply divided over a possible referendum on Brexit. It would now also be divided over the Union. Many Labour MPs feel as strongly about Scottish independence as they do about Brexit, and many would refuse to consider a referendum on independence, as Ed Miliband did in 2015.

For their part, the Conservatives would try to win over the Liberal Democrats. But there is no way, after Nick Clegg's disastrous 2010 coalition with the Cameron Conservatives (after which the Lib Dems were almost destroyed) that the next leader (probably Jo Swinson) would go down that road. But she is almost as hostile to Scottish independence as to Brexit. It's a double headache for Corbyn.

Perhaps a leader of political genius, a Harold Wilson perhaps, would be able to keep the non-Tory ducks in a row, but it seems most unlikely that Jeremy Corbyn would have the personality or the negotiating skills, to cope. We could be left with the worst of all possible worlds in a parliamentary democracy: where no party is capable of forming a government.

READ MORE: Iain Macwhirter: Dark arts helped Boris Johnson see off his rivals with the ruthless efficiency of Tony Soprano

The Fixed Term Parliament Act doesn't help much here. It has no solution to parliamentary deadlock other than a general election, and no one will want yet another one. Nigel Farage will be in his element. You can imagine him standing on the backbenches, railing against the feeble political elite, demanding action as the clock ticks down to Brexit on 31st October.

He's right. Britain doesn't have the time for a full scale, all-singing, all-dancing constitutional upheaval. Someone needs to be in Number Ten if only to be around when Brussels announces that Britain has left the EU without a deal.

So, if the SNP hold the balance of power, could Nicola Sturgeon offer a “historic compromise”? Might she promise that, if Jeremy Corbyn agrees to revoke Article 50, and hold a referendum on Brexit, she will shelve (again) her call for a referendum on Scottish independence, for the lifetime of the present parliament? She might have to, because there is just too much going on to hold another referendum on Scottish independence amidst the chaos.

Mind you, supporters of the SNP in Scotland might not see it that way. Could she really abandon this opportunity to win independence – an opportunity that might never come again? Either way, come September, the Scottish National Party could be deciding not just the fate of Brexit, but the fate of the Union itself. Try swatting that away.