Margaret Thatcher became Leader of the Conservative Party by accident. Ted Heath was the very clear favourite. Yet even some Tory MPs who felt he was the right choice had felt bruised by the way he took them for granted. So the campaign pitch from Airey Neave and the rest of Thatcher’s campaign team was: “All right, Ted’s going to get it. But let’s take the chance to send him a message. If he gets a huge majority he will be more insufferable than ever.”

Labour canvassers around the country are adopting the same tactic. The message is that there is no possibility of a Labour Government – so please vote Labour, safe in that knowledge that there is no risk of it leading to a calamitous Labour victory. It is perverse pitch – and at odds with the defiance of the clique of Corbynistas in charge of Labour’s national campaign effort.  But I suspect the constituency Labour message of defeatism is working rather effectively. I have spoken to several voters this week who have said they would regard Jeremy Corbyn in Downing Street as a disaster but are still voting Labour.

The message works best where there is a sitting Labour MP seeking to be returned again. Invariably they will seek to turn the election into one about local issues. How the MP is a hard working “champion” of the area who is “fighting for you”. How they are determined to save some local hospital (which invariably isn’t genuinely under threat of closure anyway).  There will be lots of pictures of the Labour MP looking caring and responsible – with no mention of Corbyn.

Yet a General Election is fundamentally about national issues. We are making a decision as to who should form the Government of our country. It seems frivolous – bordering on the irresponsible – for anyone to vote for an outcome that he regards as against the national interest on the basis that there is only a one or two per cent chance of a victorious outcome for the Party he is voting for.

My own hunch is that the Conservative majority could be even greater than the opinion polls suggest.  James Forsyth writing in The Sun this morning says:

“National opinion polls can only tell you so much about British elections. What really matters is what happens with certain voters in key seats.

This is why the Tory ground campaign is all about what they call “TVT” – or Targeted Voter Turnout – at the moment.

The formula is based on the work of Jim ­Messina, who ran the 2012 presidential ­campaign for Barack Obama and played a key role in the Tories securing their surprise majority in 2015.

This means reaching out to those voters in key seats who the Tories’ magic formula has identified as potential switchers to them.

Tories on the ground report “amazingly good returns” using this data. Conservative campaign headquarters remain desperate, though, to play down talk of a Tory landslide.”

There will be other tactical considerations that will help the Conservatives. In Scotland some Labour supporters may respond to a plea to vote Conservatives to defeat the SNP. Perhaps some Labour supporters across Britain will have noted the suggestion that Corbyn will try to stay on as Labour leader if the Party secures an increased share of the vote. They may decide the best way to help Labour is to vote Conservative and make sure the defeat is so crushing that Corbyn is forced out.

So let us be honest and concede that the risk of a Labour victory is indeed tiny. Say one per cent. The simple plea to voters should be that however small the danger might be, it would be quite wrong to vote in a way that would increase it.