Perhaps the biggest problem that the Conservatives face at the coming election is opinion poll leads such as most of those below, from this morning’s paper’s.

Conservatives: 50 per cent (ConRes, Sunday Mirror), 48 per cent (YouGov, Sunday Times), 45 per cent (Opinium, Observer), 40 per cent (Survation, Mail on Sunday).

Labour: 26 per cent (Opinium), 29 per cent (Survation), 25 per cent (ComRes), 25 per cent (YouGov).

Liberal Democrats: 12 per cent (YouGov),  11 per cent (ComRes), 11 per cent (Opinium),11 per cent (Survation).

UKIP: 11 per cent (Survation), 9 per cent (Opinium), 7 per cent (ComRes), 5 per cent (YouGov).

So why should Theresa May worry at polls showing her party scooping up perhaps half the vote? Because of their possible effect on turnout.

A core Tory ploy in general elections when in government is to seek to frighten voters with the possibility of Labour winning.  Sometimes it works (as in 2015), sometimes it doesn’t.

The problem this time round is that many voters have looked at Labour since Jeremy Corbyn became its leader, and looked at Corbyn himself, and decided that he can’t be Prime Minister and that Labour won’t win – and shouldn’t.

This belief is faithfully reflected in the four polls above.  The more Conservative voters see poll headlines like these, the more likely they are to believe that Labour can’t win.  The more they believe that Labour can’t win, the less likely they are to vote.  And the less likely they are to vote, the better Labour are likely to do – and the Liberal Democrats, too.

That last point could turn out to be important.  The Liberal Democrat vote can reasonably be expected to go up, boosted by former Remain voters who are still angry about last June’s referendum result.  While that is likely to help the Conservatives in blue-red marginal seats, it can only harm them in blue-yellow ones.  So polls like today’s will irritate rather than enthuse Tory candidates in south-west London and the south-west of England.

All of which explains why Downing Street and CCHQ will both be muttering quietly to themselves today: can we have lower opinion poll ratings, please?