IT'S not quite an iron law of UK politics, but almost: a Prime Minister on course for a crushing defeat at the next general election will generally try to delay that election for as long as possible in the hope that something will turn up.

As long as his or her Commons majority is substantial, that would generally be a perfectly feasible strategy to attempt, because MPs would normally be bound to back a confidence vote in the government to save their own skin.

So, when it appears that Rishi Sunak cannot risk turning the vote on his Rwanda plan into a confidence vote because some Tory MPs would actually be prepared to take the nuclear option, the only conclusion to draw is that his hand is abnormally weak even in the context of his polling plight.

In spite of some signs of the Labour lead narrowing a touch, the Tories remain around fifteen points behind on an average of the most recent polls, which is likely to translate to a landslide defeat for Sunak if, as the speculation has it, he feels compelled to hold an election as soon as the spring simply because the Tory party can no longer be controlled.

There is also the danger, of course, that the divisions triggered by Robert Jenrick's resignation and the disunity over the Rwanda vote could see the Labour lead start to grow again.

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It's not that a majority of the public agree with Jenrick's critique of Sunak's stance, in fact what polling evidence there is suggests the reverse is likely to be true.

Sunak's logic that there is little point in stepping outside the European Convention on Human Rights if that will lead to Rwanda pulling out of the scheme will seem inescapable to most voters.

But divided parties tend to be punished, and it may also be that some of the minority of voters who share Suella Braverman's "dream" of seeing migrants deported to a distant African country may be tempted to drift off to Reform UK.

It's no secret that Braverman continues to covet Sunak's job, and while it's likely her next bid will only come after a general election defeat, it's still possible that there will be enough letters sent to the 1922 Committee to trigger a vote of confidence in the Tory leader himself.

The chances are that he would survive, but the process would further damage his own public standing and that of his party. If he was ousted, on the other hand, the Tories would theoretically have the opportunity to start afresh under new leadership, but in truth they would have become such a laughing stock by installing their fifth leader in five years that the scale of the Labour landslide might be even greater.

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None of this offers much comfort for the independence movement in Scotland.

The most effective recruiting sergeant for the Yes camp is Tory rule, but perhaps more importantly, the SNP themselves have won majorities in Westminster elections in part due to the seeming pointlessness of voting Labour.

That trump card seems to be disappearing for the foreseeable future.

It's arguably odd, then, that the SNP are approaching the general election with a relatively conservative strategy that aims to avoid scaring moderate voters, as if they think the default is that people will continue voting SNP as long as they're not given any particular reason not to.

In reality, the default in a Westminster election may well be Scots voting Labour to help kick the Tories out, and to avoid that being the decisive impulse, the SNP may need to capture voters' imaginations with a much more dramatic offer on independence than they are currently planning.