Years ago, I remember one of Alex Salmond’s colleagues telling me that the former first minister resembled Charles Dickens’ character Micawber.

Known for his belief that “something will turn up”, Micawber became synonymous with someone who lives in hopeful expectation. This, down the years, was regularly asserted by Salmond and his party, a dogged belief that some future event would serve to boost support for the party and independence.

Only most of the time it wasn’t true. Take opposition to Thatcherism in Scotland, often claimed to have boosted support for the SNP. In fact, the party actually performed better shortly before she became Leader of the Opposition in 1975. Throughout the decade Thatcher was PM the SNP polled in the mid-teens.

The same script was repeated in relation to Blairism, which Scots apparently “rejected” by voting New Labour in large numbers. Still, support for the SNP stagnated in the high teens at Westminster and about 10 points higher for Scottish Parliament elections.

Support for independence, meanwhile, hovered at around one-third for most of this period, seemingly immune to the SNP’s Micawber Principle. Even the Iraq War didn’t make much of a difference.

What actually boosted support for the SNP and independence was the 2014 referendum. Suddenly the dynamic shifted and, shorn of party politics, independence gained around 15 points in the space of a few years while, at the 2015 election, the SNP managed almost 50 per cent of the popular vote. Nationalists had long argued that a big chunk of Labour voters would, come the crunch, back independence, and it turns out they were correct.

But since then, support for the SNP has declined at the last few elections, while support for independence is stuck at around 45 per cent. Impressive, certainly, but still not enough. So, once again, there’s lots of Micawberish sentiment around. Something, it’s regularly asserted, will turn up and take that figure across the 50 per cent mark.

“Westminster austerity” was supposed to do the trick, as was the prospect of “perpetual” Tory rule and, of course, Brexit. But while the last of those did result in movement from No to Yes, it was cancelled out by voters going in the other direction, too. Earlier this year, it was also widely predicted that Theresa May vetoing a second independence referendum would appal enough Scots to benefit Yes, but it did not.

Now Nationalist Micawbers appear to have settled upon two ongoing events providing salvation, Brexit chaos and “decaying” Westminster politics. Both, however, strike me as wishful thinking.

First, like independence, Brexit cuts across party lines and therefore isn’t a reliable basis for boosting a particular party or constitutional project. Logically, for example, Remainer outrage should have benefited the Liberal Democrats in June’s election, but they remained in the doldrums. Similarly, the behaviour of Yes Leavers significantly harmed the SNP in the north-east.

Combine that with the Scottish Government’s own indecision about precisely what it intends to do vis-à-vis the European Union should Scotland become independent, and it’s difficult to see how further Brexit chaos ends up increasing Yes support.

The second analysis, “chaos” at Westminster, dovetails with the first. A few days before Salmond arguably crossed a line by unveiling a new chat show on the Kremlin-backed Russia Today, he was telling a meeting of the Scottish Independence Convention that in the past three decades he had “never seen the British state in a state of more disorientation and chaos”, thus the “timing” had “never looked better for the national cause of Scotland”.

Salmond’s rationale was that an SNP pledge to hold a referendum “at the point of hard Brexit” or at the point of a transitional arrangement beyond a hard Brexit, would offer what he called an “island of certainty in a sea of confusion”, which would help them win majority support for independence.

This is widely believed, but it ignores two important points. First, Salmond’s scenario only works if independence carries no risks or “confusion” of its own and, second, it assumes an unimpeded ability to call and hold a second plebiscite. Sure, Theresa May’s “now is not the time” cry earlier this year was deliberately ambiguous, but there’s little evidence she’ll budge anytime soon, and certainly not before a UK election due in 2022.

The Micawber Principle, meanwhile, extends beyond the SNP. In Catalonia, for example, it was generally assumed Spanish police violence would boost support for the region’s own independence project, but that doesn’t seem to have transpired. Pro-Spain rallies are well attended, the polling little changed.

And, closer to home, Tony Blair irritated some in his own party by observing that given the “mess” afflicting the minority Tory government, Jeremy Corbyn ought to be enjoying a poll lead of 15-20 points rather than being neck and neck with the Conservatives.

Which brings me to the perpetually “embattled” Prime Minister. Mrs May’s problems are legion; how, people ask, can she possibly survive? Surely the great British public are increasingly appalled by recent events and will desert the Tories en masse, concluding that that nice Mr Corbyn would make a much better premier.

Only it isn’t true. A recent YouGov poll showed that, on the contrary, the proportion of voters who think May makes the best PM has actually increased since last month. It might be comforting for Labour (and the SNP) to believe that Westminster decay will significantly move the dial but, thus far, there’s little evidence it actually has.

But the central weakness of Micawberism is its passivity. The belief that “something will turn up” divorces the SNP and Labour from actually making the case for independence or a Corbyn government, and instead puts their faith in external events determining their electoral fortunes. If only it were that easy.