The American academic and pollster Larry J. Sabato famously said “every election is determined by the people who show up”.

And that is exactly what is worrying some Conservative MPs in England right now.

By rights they should be cock-a-hoop.

A poll earlier this week suggested that the party was on course to increase its majority to 100 seats.

A string of surveys have put them an astonishing 20 points ahead of their nearest rival, Labour.

Polls also suggest that Theresa May is viewed by much of the public as a much more Prime Ministerial figure than Labour leader Jeremy Corbyn.

But Labour's poor showing is also causing some headaches and questions.

Some believe that problems around turnout could leave the party with a Commons majority much smaller than predicted.

For some Conservative MPs, in safe seats it has to be said, there is, in one way, too little tension in this election.

Many voters believe that Theresa May will win easily.

That poses a key motivational problem, how do the Conservatives convince their supporters to vote.

When it comes to it on June 8 will they sit on their sofas, or in the garden, instead of dragging themselves to the polling booth?

Will those who have holidays already booked bother to fill out the form to secure a postal vote?

Or will they think to themselves that there is no need because the Conservatives "have this in the bag?”

The fear is that many could risk counting their Tory chickens before they hatch.

Or, to put it another way, will the political postmortem after this election centre not on 'shy Tories' but on 'complacent Conservatives'?

The issue is less of a problem in Scotland, where the Conservatives are mainly battling the SNP rather than Labour or the Liberal Democrats.

But fears over what could happen in England led Theresa May to try to talk up the chances of a shock result yesterday.

During a visit to a factory in her constituency she warned that the outcome of the election was "not certain".

One of Mrs May's main campaign tactics in this election depends on voters believing that the result could tight.

In recent days she has warned of a “coalition of chaos” between Jeremy Corbin’s Labour and other parties, including the SNP.

The Tory leader is attempting to reheat one of her party’s most successful arguments from the 2015 general election.

Then David Cameron convinced lots of voters that they had to back him to prevent the SNP 'pulling the strings' of a Labour government.

The attack ads swiftly became notorious.

One even depicted Alex Salmond as a pickpocket.

The Conservative message was clear: The SNP would hold Labour to ransom inside No 10.

But in 2010 the polls suggested that Westminster was heading for a hung parliament.

Convincing voters over the next seven weeks that the result of Mrs May's snap General Election is "not certain" will be a harder sell.

But she knows that the more she can convince her Tory voters that there is a chance she might be kicked out of Downing Street the bigger her majority could be on June 9.