Lord Ashcroft’s poll of Labour’s heartland failure proves one thing: telling people that voting SNP will deliver a Tory government simply bounces off.
Four out of five Scottish Labour supporters who are determined to vote SNP want a Labour-SNP coalition at Westminster after May.
Voting for the SNP will produce exactly the opposite effect.
So far, Labour has been unable to convince voters of that essential truth.
Or, more probably, voters are not listening any more than they monitor the daily fluctuations in price of a barrel of oil.
But if the SNP is the choice the consequence is almost certain - Scotland will find itself opening the Downing Street door to David Cameron.
That is not the result Labour switchers want, though it is the outcome that best suits the grateful recipients of their support, the SNP. A Tory government, an EU referendum and constitutional chaos is the SNP menu.
The Ashcroft poll drops the pretence. It is Middle Scotland, not Middle England, that will decide who holds the No 10 keys.
Westminster number-crunching has Labour and the Tories in a dead heat. With neither having majority support jostling for the most seats becomes a crucial factor.
What polling does not examine is how coalitions are formed.
In a hung parliament David Cameron will have squatting rights in Downing Street. With the most seats, though with fewer options, he can make the first move for minority or coalition rule.
There is no logic to the suggestion that a Labour minority government will be magicked up by voting SNP. You can’t vote for a coalition, but the trick works in a nation divided along referendum lines.
Ashcroft’s English marginal polls opens the Downing Street gates to Miliband. But it is a long walk to the fabled black door.
If Labour loses 40 seats in Scotland it needs to win an impossible 88 in England to have a majority.
Haemorrhaging tartan blood will leave Labour short of being the biggest party, the target it can best expect.
If Scottish voters feel angry enough to wipe out Labour the result will be a divided left, not a progressive coalition.
Scotland would be a hapless bystander to another right-wing government and, given the scale of proposed Tory cuts, Scots would suffer.
Putting the constitutional future on the slates again is ideal for the SNP, but not for Scotland’s poor. That’s the Ashcroft lesson.