MSPs return to Holyrood today. The First Minister, Nicola Sturgeon, is due to unveil her legislative plans for the next year – the last full year her government has left before she and her fellow MSPs are due to face the electorate in May 2021.

Yet there has been speculation that Ms Sturgeon might want to bring forward the date of the next Scottish Parliament election. 

If in the next few months the UK leaves the EU with deleterious consequences that have an immediate impact on voters and boost support for independence, a contest held early next year could provide the SNP with an ideal backdrop against which to secure another pro-independence majority.

 Such an outcome could in turn pave the way to a Westminster-sanctioned second independence referendum, as both the former Scottish secretary, David Mundell and the Labour leader, Jeremy Corbyn, have acknowledged.

However, the Scottish Parliament is meant to hold its elections on a fixed cycle. The First Minister cannot simply call a ballot at a time of her choosing. 

True, there can be an early election if two-thirds of MSPs vote for one, but there is no guarantee that Ms Sturgeon could win such a vote. Otherwise, an early election is also called if the First Minister resigns and the Parliament fails to install a successor within 28 days. 

This latter provision has led to the suggestion that Ms Sturgeon could precipitate an early ballot by resigning as First Minister and presuming that Holyrood would not find somebody to fill her shoes.

Trouble is, holding an early Holyrood election would not buy the SNP any more time. However instigated, another election would still be due in May 2021 – a requirement in the Scotland Act designed to discourage any Scottish Government from trying to engineer an early contest. 

Meanwhile, the ploy of Ms Sturgeon resigning might be thought to be taking a leaf out of the Dominic Cummings’ playbook of constitutional manoeuvring. Yet arguably Scotland should not be having to wait another 20 months before it has the chance to vote for a new bunch of MSPs. 

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The fixed cycle of Holyrood elections in the devolution settlement provides for an election every four years. The last Scottish Parliament election was held over three years ago in May 2016. So if we were keeping to the regular cycle, the next Scottish Parliament election should take place next year.

Why, then, is the election scheduled for 2021 instead?

Initial responsibility lies with Westminster. When it passed its own Fixed Terms Parliament Act in 2011, it provided that Commons elections should be held every five years. 

That meant the next Westminster election was due to be held in May 2015, when the next Holyrood contest was due to be held. Everyone agreed it was a bad idea to have a UK election and a Scottish Parliament election on the same day, so Westminster legislated to postpone the 2015 Holyrood election until 2016. The Scottish Parliament had its first five-year session.

This, however, was no more than a stopgap measure. Given Holyrood’s usual four-year cycle, a Scottish Parliament election would now be due in 2020 and clash with the Westminster election that was now scheduled for that date. 

In the meantime, the Smith Commission that was established shortly after the 2014 independence referendum recommended both that Holyrood elections should not take place on the same day as a Westminster ballot and that Holyrood should become responsible for decisions about its own election.

These recommendations were eventually enshrined in the 2016 Scotland Act. 
However, even before that Act had reached the statute book, Holyrood sought and was granted the authority by Westminster to pass early in 2016 another stopgap measure –  to delay the 2020 election until 2021. 

This ensured another five-year parliament, albeit one that this time was signalled to voters in advance of them going to the polls.

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It is that decision which means that MSPs are not due to face the electorate next year. However, the question that now arises is whether that decision should still stand. 

For when two years ago Theresa May came back from a walking holiday in Wales and succeeded in persuading two-thirds of MPs to vote for an early election their decision – in contrast to the position in respect of an early Holyrood ballot – meant that the subsequent election would not be due for another full five-year term, that is, May 2022. 

The clash between a 2020 Holyrood election and a 2020 Westminster ballot against which the Scottish Government had sought so speedily to legislate was removed from the schedule.

There would, then, seem to be a pathway that would allow the SNP to hold a Scottish election next year should it so wish – and in a way that would mean the next Parliament would still have a full four-year term. 

The decision to delay the next election until May 2021 could be reversed and a ballot rescheduled for next May. Yet even though two years have elapsed since it became clear that a scheduled Westminster election no longer stood in the way of restoring the regular four-yearly rhythm of Scottish democracy, no intimation has been given that this might happen. 

However, perhaps Ms Sturgeon will surprise us in her speech today – or should we simply bear in mind that it would be unusual for a politician to opt for an early appointment with the electorate.

John Curtice is Professor of Politics, Strathclyde University