The main focus in this election has been the Brexit battlegrounds of England, where most expect the Commons majority that Boris Johnson needs to be won or lost. But this election is for a UK parliament, not an English one, and its outcome also depends on choices in the other three home nations, where arguments over Brexit are cross-cut by older cultural and constitutional fault lines.

The Scottish Conservatives go into this election defending 13 seats, following their surprise surge in 2017. The party was widely expected to lose most of these, as the SNP recovered ground, and opposition to Brexit and Johnson encouraged a Scottish reversion to anti-Tory voting habits following Ruth Davidson’s departure as leader.

But the most recent Scottish polling has called this assumption into question. The Conservatives are presently holding firm on their 2017 vote, giving most of their Scottish MPs a fighting chance.

The Conservatives’ Scottish strength derives from their position in the nation’s dual constitutional conflict over Brexit and independence. Scottish voters define themselves as much, if not more, by their views about independence from Westminster as independence from Brussels. These two existential divides cut across each other.

This has created problems for the locally dominant SNP, whose pro-independence, anti-Brexit stance causes friction both with the majority of pro-union Scots and with the fifth or so of Scots who backed independence in 2014 but also backed Brexit in 2016.

These tensions between independence and Brexit have allowed the Conservatives, long pariahs in Scotland, to rebrand themselves as the party of union and Brexit. Johnson’s Brexit-focused campaign may alienate Scotland’s Remain majority, but it appeals to the four in 10 Scots who voted for Brexit.

Johnson’s decision to oppose a second referendum also plays well with pro-union Scots, still a majority of Scotland’s electorate overall. Support for both the union and Brexit tends to be stronger in the seats the Conservatives are defending.

The SNP is gaining support overall by pushing independence and opposing Brexit, yet by doing so it may also be helping the party most firmly opposed to both these stances hold on to crucial seats.

Stuck in the middle is Labour, whose appeals for compromise find few takers in the current environment, and looks set to fall below even its calamitous low ebb in 2017. The long Scottish Labour hegemony looks far away indeed.

Labour has dominated Wales for even longer than it held sway in Scotland, winning the last 26 general elections. It may pay a price for this dominance, as two decades of rule in the Welsh Assembly make Welsh Labour a prominent target for the populist resentment mobilised by Brexit.

The Conservatives hope they can mobilise this resentment to secure gains in a Brexit-voting country with many marginal seats. Early polls pointed to a historic Tory surge, but Labour appears to have recovered recently as Welsh voters’ attention swings back to domestic issues such as health, where local suspicions of the Conservatives run deep.

Older conflicts also cut across the Brexit divide in Wales. Nationalist sentiment in the rural, more Welsh-speaking areas is mobilised by Plaid Cymru, while the Liberal Democrats had strongholds in Wales for more than a century before being wiped out at the end of the Conservative-Lib Dem coalition. The two parties have made local “Unite to Remain” alliances to maximise their prospects this time. The Liberal Democrats hope to hold Brecon and Radnorshire, gained from the Conservatives in a byelection in August, and advance in neighbouring Montgomeryshire, Liberal for most of the 20th century.

Plaid will be hoping that Unite to Remain alliances will help it hold off the Conservatives in Dwyfor Meirionnydd and boost its chances in the three-cornered fight for the Ynys Môn constituency.

The tangled mix of old and new conflicts is even more complex in Northern Ireland. Deadlock between the EU and the British government over the Northern Ireland border has been a persistent stumbling block in the Brexit negotiations, while deadlock between the DUP and Sinn Féin has left Northern Ireland itself without a functioning devolved government for nearly three years.

Voter frustrations over the dual impasse may boil over in this election – the one recent poll we have suggests a swing against both of the locally dominant parties. Shifting local allegiances have broader implications – the DUP is broadly pro-Brexit though opposes Johnson’s deal, while Sinn Féin’s opposition to Brexit is politically impotent as it doesn’t take its Westminster seats. If there are gains for either the SDLP or the Alliance, this would add reliably Remain-supporting MPs to the Commons.

The Conservatives may do well enough in the Labour Leave heartlands to secure a majority without looking beyond the borders of England. But their advance in this territory is precarious and vulnerable to even a modest narrowing in the polls. Every Tory seat retained in Scotland, or gained in Wales, is a seat less needed from England’s Brexit heartlands, while every win for the SNP, Plaid or the SDLP is an advance for the Remain cause.

The Brexit election could be decided by voters who see much more than Brexit at stake.

Rob Ford is a professor of politics and editor of Sex, Lies and Politics