IT is arguably the most important General Election of the last 50 years, with nothing less than the fate of Brexit and the state of the union at stake.

We know Scotland’s 59 seats will be a crucial, perhaps even determining, factor in both these era-defining issues. We also know the election campaign being fought in Scotland is very different to the one taking place in England.

What is much less apparent with four-and-a-half weeks to go until polling day, however, is where Scots will place their crosses on December 12.

Despite this, you’ll still hear many London-based commentators echo a narrative that assumes the SNP will win 50 seats – mostly at the expense of the Scottish Tories – a result that would take the party back (almost) to 2015 levels of representation at Westminster.

But with little new research on voting intentions conducted in Scotland for months, there is no hard evidence to back up these assumptions.

READ MORE: How contenders in three key Scottish marginals are framing their campaigns ahead of election

“There are many reasons to be cautious about that sort of prediction," says independent polling expert Mark Diffley, "not least of which is the fact that national seat predictors assume all seats behave in the same way. Sensible people in the SNP are playing down the 50 seats narrative and managing expectations.

“If you put the last voter intention numbers into a seat predictor, it comes up with around 50 seats for the SNP. Using national indicators, you might conclude that all the Conservative gains made in the 2017 election in the north-east of Scotland will go right back to the SNP. But not all seats will follow a national swing in this way.”

Then there’s political geography, which plays a part in determining how each of the parties frames its campaign. Diverse areas of the country have different, often competing, priorities and party strategists desperate to secure votes are frantically working to appear in tune with all of them.

“The campaign run by parties in the north-east will be very different from the one they run elsewhere, more focused on Brexit," says Diffley. "Then there’s the Brexit Party to consider – it could certainly take votes from the Conservatives.”

The picture is made even more complex by the large number of marginal seats – some of which are among the most marginal in the UK – in Scotland. In 2017, 14 constituencies were won by a majority of less than 1,000, while two-thirds require only a five per cent swing to change hands.

“Marginal seats present opportunities and risks for all the parties, and by their very nature are difficult to predict,” he says. “There could be surprises in any one of them, where results go against the national picture.

“Turnout is another crucial consideration, especially in those marginals. The SNP needs to get people who voted for it in 2015, but stayed at home in 2017, back to the polling booth.

“None of the parties should take anything for granted.”