The contest for Aberdeen South, a constituency that spans urban social housing and detached homes with sculpted gardens, has been dominated by one topic: the future of North Sea oil and gas.

The drama gripping the Labour party at Westminster and Andy Burham’s nascent leadership pitch in Makerfield barely affects this byelection, which also takes place on Thursday. The vote is touted as a straight fight between the Scottish National party and the Conservatives, and one in which energy policy dominates.

Aberdeen South includes the port where vast oil rig support vessels tower over the quayside, and to the west borders the River Dee as it winds past plush villas in outlying villages through the city into the docks.

Richard Thomson, a former MP and council leader who is attempting to retain the seat for the SNP, puts it this way: “If you don’t work in the energy industry, you will know plenty of others who do – your family and your friends.”

The cost of living crisis and questions about the SNP’s fitness for government after the scandal of Peter Murrell’s theft of £400,000 in party funds flare up too on the doorstep. But with oil and gas jobs being shed at a significant rate, the byelection is largely a contest between oil fundamentalists and oil pragmatists.

Pushed hard to the right by the surge of Reform UK, the Tories are now fundamentalist advocates of maximising oil and gas extraction to, they say, protect jobs, increase revenues and improve Britain’s energy security.

That security claim is widely rejected by energy experts who point out the oil is sold on the open market, which also sets energy prices, but Kemi Badenoch, on her third visit to the seat on Tuesday, is undeterred. Voting Tory would give the sector a “kiss of life”, the Conservative leader says.

The Tories believe they can pull off an unlikely victory: defeating the SNP in its heartland, winning one of the few Westminster seats held by the nationalists in a rout by Labour at the 2024 general election.

They are focusing hard on tactical voters hostile to the SNP, while attacking Reform for splitting the anti-SNP vote. A narrow 1,200-vote majority for the SNP in a contiguous Holyrood seat in May makes them optimistic Badenoch can pull off a morale-boosting Tory win.

“There’s going to be a lot of tactical voting on Thursday, whether that’s coming from people that voted Reform last time or even people that voted Labour. This is our opportunity,” says Douglas Lumsden, the Tory candidate, who also stood for the seat in 2019, coming second behind the SNP on 36% of the vote.

Aberdeen South is one of two Westminster byelections on Thursday called after SNP MPs won seats in the Scottish parliament. Scottish legislation forbids MSPs from sitting in other legislatures, so Stephen Flynn, the then SNP Westminster leader, quit as MP for the constituency.

The second byelection, to succeed Stephen Gethins in Arbroath and Broughty Ferry, is seen as such a safe SNP seat that no other party is seriously contesting it.

In Aberdeen South, the SNP tries to steer a delicate line between defending North Sea jobs while bolstering renewables on climate and investment grounds.

The surge for Reform UK in the north-east, fed by voter anger over energy jobs losses, and the Tories’ pro-oil shift, has influenced the SNP too. It has diluted the very strong stance taken by Nicola Sturgeon, the then first minister, in 2019 on declaring a climate emergency and a presumption against new drilling.

The SNP, says Thomson, supports new drilling, but only if a licence passes the UK’s climate compatibility tests. He argues that the Tories, despite their recent maximalist stance on drilling, are “no friends to the oil and gas industry”.

The SNP is telling voters the Conservatives introduced the energy profits levy – and that about 70,000 North Sea jobs were lost under the Tory government. Lumsden counters that the SNP voted for that levy, which has now served its purpose. “Things have changed now. There is no windfall to tax,” he says.

Behind this dispute sits worrying statistics. Aberdeen South is a relatively prosperous constituency. Official data shows its average weekly wage is £802 compared with the Scottish average of £776, while its relative child poverty rate is 7.8% against 12.3% for the whole of Scotland.

But with the energy sector shedding about 1,000 jobs a month, universal credit take-up is climbing, increasing by 30% since April 2022, with almost 10,000 local claimants and 8,800 families needing state benefits. House values have also plunged, leaving some in negative equity.

About 500 homes in the urban neighbourhood of Torry, a pocket of poverty, are bedevilled by crumbling Raac, a cheap lightweight alternative to traditional concrete. The council has told residents to vacate, saying the buildings are at risk of collapse, prompting a conflict over compensation levels.

Thomson believes the Tories are floundering on the cost of living. They showed no initiative or compassion in government and have been “insignificant” as the opposition, he says. Lumsden counters that the Tories’ oil policies would increase jobs and prosperity.

The Murrell affair hovers over the contest. The SNP argues its former chief executive’s guilty plea has reduced the scandal’s significance, or that voters sympathise with the party’s assertion that it was the victim.

“Most of the folk that I’ve spoken to in the city have shared my anger at what happened to SNP members who’ve had their cash stolen,” Flynn told the Press and Journal on Tuesday.

Lumsden disputes that, saying: “A lot of voters across Aberdeen see this whole episode as making the SNP not trustworthy. There have been repeated attempts to call on some sort of investigation to see who knew what within the SNP, and that’s all been swept under the carpet by [Scotland’s first minister] John Swinney. So that’s having a negative impact on him personally. That’s what we’re hearing on the doorsteps when we talk to normal voters.”