It is tempting simply to repeat, as this third week of election campaigning nears its close, what we wrote in week two.  Which itself repeated what we said in week one.  Bad weeks usually don’t matter when it comes to polling day.  Nor do bad campaigns.

As we move from the first leaders’ debates to manifesto launches, all this is still true – and would be, even had Jeremy Corbyn broken clear in Tuesday’s debate, which he didn’t; and even if Prince Andrew had not generated some real royal news, thus reducing election coverage.  This development should turn out to be useful to the campaign’s front runners – the Conservatives – because it reduces Corbyn’s opportunity to shift the dial.

Politicos poll of polls shows the Tories with a 12 point lead over Labour.  The latter hasn’t led in a single UK-wide poll since late July.  Electoral Calculus currently predicts a Conservative majority of 72The new Ashcroft polling dashboard finds Lord Ashcroft’s new dashboard finds a triple Tory win: Johnson beats Jeremy Corbyn as best Prime Minister; the Tories are ahead of Labour if voters are forced to choose between them, and Johnson and Sajid Javid are more trusted on the economy than their Labour counterparts.

Put all that together, and the Electoral Calculus estimate might seem to feel about right.  But there are good reasons to believe that it may not be.

One way of thinking about this election is as a kind of slot machine.  It must turn up three lemons, as it were, for the Conservatives to win big.  These are: Scotland, where the SNP is the main competition; the Leave-voting Midlands and North, and Remain-backing London with its prosperous hinterland.  This is admittedly a very crude picture, and there are other important geographical contributors – such as Wales, where the contest is partly blue v red, and the South-West, where it is largely blue v yellow.

If one of those lemons doesn’t come up, a big Tory majority probably won’t be realised.  If the Party is all but wiped out in Scotland; or if soft Remain voters back the party most likely damage the Conservatives in each south-eastern seat, or if old class loyalties stick in the North and Midlands, any Tory majority looks to be quite slim.  If two lemons don’t show up, Jeremy Corbyn is set to become Prime Minister.  (Or: if one appears, it’s curtains for Johnson.)

Furthermore, a boundary review is now grossly overdue, and the Conservatives tend to pile up votes in seats they already hold.  Put all that together, hold your finger to the wind and cross yourself for luck…and a Tory majority of, say, 15 seems just as likely as Electoral Calculus figure, which takes no account of these variations.  Or more likely, come to think of it.

We are a long way away from polling day, and much may change.  But just for a moment imagine that Johnson came back to Downing Street with a position only slightly improved on that held by Theresa May after the 2017 poll.  Would there not be a palpable sense of Tory disappointment?  And in this era of more frequent backbench rebellions, would not Johnson’s room for manoeuvre be only slightly improved?

There is a danger that good headline poll results are helping to create a sense of Conservative expectation that is getting ahead of the electoral facts.