A narrowing of the polls in the independence referendum this week has led to Cameron, Miliband and Clegg frantically travelling back and forth to Scotland to shore up the no campaign. The vote on 18 September will affect the UK permanently, regardless of result, but what exactly could a yes vote mean for Labour?

The most obvious impact on Labour of a yes vote would be simple: it would be deprived of a majority in May’s general election. In 2010, Labour won 41 out of 59 Scottish seats, showing the blunt arithmetic of a yes vote – Labour would presently lose in a UK-wide election without Scottish votes.

Ironically, by trying to drive Conservative rule out of Westminster, the Yes votes of Labour members in Scotland could actually increase the likelihood of Conservative dominance by denying Labour the three dozen seats needed for a parliamentary majority. It’s worth noting that David Cameron would have had a majority of 21 seats in 2010 if Scotland had been independent.

Deprived of Scotland and strong in northern heartlands, a Labour party following a yes vote would zone-in on the south east; a necessary move to win a majority.

Without Scotland, the Labour Party machine would also tilt very much southwards. Although Labour did well in London in the European elections, its performance in the south east as a whole was less inspiring. The party has tried to remedy this “Southern discomfort” since the narrow defeat it suffered in 1992. Deprived of Scotland and strong in northern heartlands, a Labour party following a yes vote would zone-in on the south east; a necessary move to win a majority.

A yes vote could also see Miliband’s leadership come under threat. Some in the party may question why the party has been blind to this threat for so long, or ask why the Party is so lop-sided in its appeal, making it subject to such a massive fallout. Labour’s shadow team would also be impacted, with Scottish MPs Jim Murphy, Gregg McClymont and Pamela Nash lost to a future Labour team.

Scotland has a history of providing Labour ministers and Labour leaders, from Gordon Brown and Alistair Darling, to John Smith, Ramsay MacDonald and, in its formative years, leaders Arthur Henderson, George Barnes, and William Adamson. Labour has an emotional attachment to Scotland and the deep impact the country has had on the Labour movement (just look to Gordon Brown’s biography of his hero James Maxton for evidence of this).

Ideologically, the change would also have an impact on Scottish Labour. Free from a UK-wide party, Scottish Labour may become ideologically more distinct. In positioning itself against an SNP that advocates free personal care, free prescriptions, high public spending and university education far cheaper than for students south of the border, Labour may take a sizeable shift to the left. Therefore, in order to outmanoeuvre Alex Salmond, Labour’s Scottish high command may have to undertake a serious policy and positioning rethink.

The referendum will be giving both David Cameron and Ed Miliband sleepless nights for different reasons. For Cameron, a yes vote could bring about a collapse in authority, a leadership challenge and the end of the party’s unionist ideology. For Miliband and Labour, the ideology is more nuanced (solidarity rather than a constitutional union), and the cold hard arithmetic that could deprive Labour of power not just in 2015, but for the foreseeable future.

Labour voters south of the border are praying for the solidarity Ed Miliband and Gordon Brown speak of. Without Scotland, Labour could be finished.