Why the Conservatives' by-election win over the SNP in Aberdeen South is significant

The SNP defended two Westminster seats vacated by politicians joining Holyrood this week.

One went to script, the other did not.

The SNP held Stephen Gethins' former seat of Arbroath and Broughty Ferry, in the Dundee heartland of Scottish nationalism, but it lost in Aberdeen South, where Stephen Flynn's departure has delivered the first Conservative by-election gain in Scotland for nearly 60 years.

The Conservatives won 49.5% of the vote, up 25.1%, a vote gain bigger than the party achieved in its 2021 Hartlepool by-election win, and the biggest achieved by the party at any by-election since 1945.

Indeed, it was the best vote share for the Conservatives in this seat since 1964.

On any other night, such a stunning gain by a party lately confined to the margins of Scottish politics would lead the headlines.

Yet, while it was overshadowed on the night by Andy Burnham's return in Makerfield, this result, plus gains from Reform in local council by-elections, might hint at a turning of the tide for the Tories after a long post-general election slump.

In some respects, this was a return to form for Aberdeen South, a seat which features some of the wealthiest suburbs in Scotland, and which was Conservative for nearly 70 years, with one brief interruption, from 1918 to 1987.

The Tories have held it more recently, too, winning it in 2017 as part of the Scottish blue wave that year.

The SNP's long-running embezzlement scandal, and the travails of the oil industry, which formed the focus of the Conservative campaign, may both have contributed to this stunning win, the first Conservative gain at a by-election in Scotland since Glasgow Pollok in 1967.

The slump in Scottish Labour likely played a role here, too.

The Scottish Conservatives won the seat from third place, after Labour surged to overtake them in the 2024 general election.

That surge was fully reversed here, as Labour suffered their eighth-largest decline in vote share across all Scottish by-elections.

Unhappiness with the national Labour government doubtless played a role, but perhaps also tactical voting by unionists who could use the Conservatives as a vehicle for registering discontent with the Holyrood and Westminster governments.

The SNP's comfortable hold in Arbroath and Broughty Ferry also featured warning signs for both incumbent governments.

The turnout was just 31.9%, the lowest in a Scottish contest in post-war by-election history.

Read more from Sky News:
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Analysis: Why Burnham's win is so significant

Unhappy nationalist voters may not have marked ballots against the SNP, but instead opted not to cast a ballot at all.

Scottish Labour also slumped in this seat, suffering their 10th largest drop in Scottish by-elections here.

Reform's vote shares in both seats set new records for Scottish by-elections, but the party has not contested many.

The party won 8.6% in Aberdeen South, coming a distant third, and in Arbroath and Broughty Ferry managed 18.2%, nearly beating the Conservatives for second place.

The Arbroath result is Reform's fourth-highest vote share in all by-elections, while Aberdeen South is the ninth best.

(c) Sky News 2026: Why the Conservatives' by-election win over the SNP in Aberdeen South is significant