PITY the Shetlander.

The inhabitants of Holyrood’s northernmost constituency have been plagued by touring politicians this summer. There is a byelection next Thursday and the SNP are throwing the kitchen sink at it, hoping to inflict a shock defeat on the Liberal Democrats.

A third of the SNP’s MSPs have visited so far, including Nicola Sturgeon (three times) and a good chunk of her cabinet. There have also been MPs, MEPs, councillors and staffers from HQ.

It’s a fascinating contest. For this is no ordinary seat. Shetland is, on paper, the toughest target in Scotland.

The byelection was triggered by former Scottish LibDem leader Tavish Scott quitting to work for Scottish Rugby.

When he won Shetland for the fifth time in 2016, he did so with 67.4 per cent of the vote. The SNP came second on 23.1%.

The Northern Isles have also voted Liberal or LibDem continually since 1950.

But while that LibDem majority looks unassailable in percentage terms, you can look at it in other ways too.

Shetland’s 17,810 electorate is the second smallest in Scotland. Mr Scott’s majority - based on a strong personal vote remember - was 4,895 in 2016 on a 62% turnout. By-election turnout is generally a lot smaller than in general elections. If it were 40 per cent, the theoretical majority would be nearer 3,150. That means the SNP could win by persuading 1600 LibDem voters to switch sides.

Then there’s the last election in which Shetland voted. In May’s European poll, the LibDems came first on 29.6% while the SNP got 25.9%. In terms of votes, the LibDems got 2001 and the SNP 1751, a difference of just 250. Turnout was 40%.

The big difference with 2016 was the presence of the Brexit Party, which got 1330 votes, or 19.8%, in May. The Brexit Party aren’t standing on Thursday, although the husk of Ukip are.

If a lot of Leavers stay home, put off by a two-horse race between Remainers, the fight between the SNP and LibDems becomes a real one. The fewer the votes in play, the bigger the scope for an upset.

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Orkney MP Alistair Carmichael this week sounded the alarm, urging Labour and Tory supporters to back the LibDems. “If we split the anti-independence vote by voting for other parties or independents, then it is possible the SNP could win this seat,” he said.

“There is a reason why, having not set foot in Shetland for three years, the First Minister has now visited three times in one month.”

Of course, scare tactics to mobilise your vote are standard for elections. But other LibDems say similar things in private. “It’ll be close,” they frown.

There is another factor that can help the SNP. Money. At national elections, candidate spending limits are based on the size of the electorate. In Shetland, the maximum allowed by law in 2016 was £32,883 over five months. But the spending limit in byelections is a standard £100,000 that can be spent in five weeks.

That kind of money - which the SNP has and the Scottish LibDems don’t - lets the SNP blitz every corner of the islands.

Motivation is also with the SNP. Winning Shetland would show the party can win anywhere. It would burst Jo Swinson’s bubble. Fighting it hard forces the LibDems to spend cash they’d rather not, drawing in subsidies from the UK party earmarked for the general election.

If the LibDems lose, they also lose their seat on Holyrood’s business bureau, which deals with chamber and committee work, as membership requires five MSPs.

So should we all wait up to the small hours on Friday to catch some Holyrood history? I wouldn’t put the cocoa on yet.

The SNP is still the under-dog, and it sounds it. “Lend me your vote,” pleaded candidate Tom Wills this week. He’s “asking for just 18 months until the next election”, the First Minister added.

The SNP’s main message has also been incoherent, hyperbolic nonsense. Unable to play the Remain card against the LibDems, it has tried to make the vote about the Prime Minister. Despite Shetland voting 56.5% Remain in 2016, Ms Sturgeon and Mr Wills are promoting guff about a vote for the SNP sending “a strong message to Boris Johnson that Shetland won’t stand for Brexit”.

Picture the scene in Downing Street. “I’m sorry, Prime Minister, but you’ve been sent a strong message. Remain voters in a Remain seat in a Remain country have swapped one Remain party for another in a Remain parliament. Nothing in Westminster has changed one jot. However, just to be on the safe side...”

The SNP sounds like a party trying to talk furiously about national issues because it’s running scared of its record on the ground after 12 years in power.

“I know there’s more work to do to improve local ferry services,” says Mr Wills of a key issue. He promises a “brighter future” if he wins. Brighter future is code for an inadequate present.

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In contrast, LibDem Beatrice Wishart has focused throughout on local issues like ferry costs, poor broadband, farming, schools and the NHS, putting the blame squarely on the SNP for all shortcomings.

As one SNP hand puts it: “The LibDems are not as toxic as they were. The Brexit thing is not going to work for us up there because they’re as anti-Brexit as we are. We’re also getting to the stage where people must feel tired of having their doors banged every night of the week.”

However byelections do throw up surprises, and if the SNP win, there is an intriguing consequence. It would tie the votes in parliament. There would be 64 in the Nationalist corner and 64 for all other parties. The Government could avoid embarrassing defeats. It would not have to watch its laws being repealed again by a united opposition, as happened with the Offensive Behaviour at Football Act.

It would also put Ms Sturgeon achingly close to an absolute majority. Another byelection or a defection and she could claim a stronger mandate for Indyref2.

Well, almost. Only 63 of those 64 votes would come from SNP MSPs. The other would rely on Mark McDonald, the former minister who quit in a sleazy text scandal. He currently represents his Aberdeenshire seat as an Independent, but normally votes with his old party.

If the SNP win Shetland, his vote would become more valuable to ministers and so give him more leverage. Perhaps, after his two-year penance, the SNP might like to readmit him, for instance? He was never expelled after all, but resigned.

If the SNP pull off an upset in Shetland, it would indeed mean a brighter future. Just not for the islanders or the rookie sent south for “just 18 months” on probation. I suspect the real winner would be the miraculously rehabilitated former pariah for Aberdeen Donside.