This article appears as part of the Unspun: Scottish Politics newsletter.

By-elections matter. The three this week definitely matter to Rishi Sunak and Sir Keir Starmer as they sniff the wind ahead of the general election.

They matter to MPs as they weigh the fate of their seats and their careers.

And they matter to MSPs as they try to calculate what it means for Holyrood in 2026.

The significance of by-elections is often exaggerated, of course.  

Of the 520 held for Westminster since 1945, only a few are famous for being genuine political watersheds. Many are infamous for odious campaigning. But they really do count. After Winnie Ewing died last month aged 92, every obituary drew attention to her seismic win over Labour in the Hamilton by-election of 1967.

It showed Labour was vulnerable in its heartlands, prefigured more SNP success in the 1970s, and confirmed the arrival of a major political figure.

“We can safely say that woman changed Scottish history,” as Alex Salmond later put it.

SNP by-election wins in 1973 and 1988 in Glasgow Govan also saw major players anointed by the electors, as first Margo MacDonald and then Jim Sillars ousted Labour.

When Roseanna Cunningham beat the Tories in Perth & Kinross in 1995 it was a harbinger of crisis for the government. Two years later, the Tories were wiped out north of the border.

The SNP’s John Mason also won the Glasgow East by-election from Labour in 2005. Two years later Labour lost at Holyrood and Mr Salmond was First Minister.

And when the Tories won the Crewe & Nantwich by-election from Labour in 2008, it was the first such gain in 26 years. Two years later David Cameron was in Downing Street. 

The Herald: Roseanna Cunningham won the Perth & Kinross byelection from the Tories in 1995 – two years later the Tories were wiped out north of the borderRoseanna Cunningham won the Perth & Kinross byelection from the Tories in 1995 – two years later the Tories were wiped out north of the border (Image: Newsquest)

But by-elections can also be false dawns. Ms Ewing was the SNP’s second MP, not its first. 

That distinction belongs to Dr Robert McIntyre, who won the Motherwell by-election in 1945, then lost the seat back to Labour three months later.

Ms Ewing’s win was remarkable not just because of where it happened but when, showing that the SNP was back as a political force after more than 20 years without a single MP.

The history books are littered with by-elections that seemed to herald a sea change but which ultimately proved to be one-offs and outliers.

The Liberals taking Orpington in 1962 from the Tories only for Labour to win the following general election; the ill-fated SDP winning Crosby in 1981 and Glasgow Hillhead in 1982; the nomadic George Galloway beating his old Labour party in Bradford West in 2012.

So what to make of the three by-elections this week?

If, as the all-knowing bookmakers predict, the Tories suffer a triple defeat, it will be the worst result for a governing party since Labour lost three by-election seats in a day in 1968. 

That cannot be put down to mid-term blues. That is historic. 

This week’s seats are scattered round the country – Uxbridge & South Ruislip near London, Somerton & Frome in Somerset and Selby & Ainsty in Yorkshire – with sizeable majorities of between 7,000 and 20,000, yet Labour and the Liberal Democrats could overturn them.

The common factor would be voters turning en masse against the Tories, unwilling to forgive Mr Sunak for the sins of his chaotic predecessors.

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At this point in the electoral cycle, it would point to a bloodbath, doubtless leading to yet more Tory infighting and a self-fulfilling spiral of decline. 

Labour and the LibDems will be cock-a-hoop. A narrative of coming doom established, the Prime Minister will start making plans to spend more time with his money. 

It will also be instructive to see the SNP’s reaction. A resurgent Labour will eat into SNP support at the general election and rob them of a Tory bogeyman.

The SNP is also likely to resist dancing on Mr Sunak’s grave for another reason.

In its 89-year history, the party has lost only one parliamentary byelection. True, it failed to gain many of its targets, but it has only lost one seat won at the previous election.

That was Dunfermline in 2013 after MSP Bill Walker was convicted of assault. 

The SNP now faces its second loss in the Westminster seat of Rutherglen & Hamilton West after a recall petition against MP Margaret Ferrier for Covid rule-breaking.

As with Walker, the party could put a defeat down to exceptional circumstances.

But after 16 years in power and questions over competence and direction, the SNP will worry it could be one of those ominous by-elections that contain a taste of things to come.

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