Dr Stuart Thomson is a Public Affairs Consultant with Bircham Dyson Bell and an honorary research fellow at the University of Aberdeen.
It is not a case of the SNP doing well in the coming election. It is only a case of how well. The emphasis so far has been on how many seats the party could take from Labour but the Lib Dems are vulnerable too.
Critically though how welcome will the SNP be in Westminster?
Recent polls from Lord Ashcroft predict a near clean sweep for the SNP.
This would make the Conservative result in 1997 look tame.
Whilst these polls are being seen by many as extreme in their findings, privately Labour believes that its seats could be at least halved in Scotland.
The chances of Labour winning large numbers of these seats back would look bleak.
The question is would they want any formal arrangement with the party that had potentially all but wiped them out?
The Prime Minister offered some of his own political advice telling Labour not to work with the SNP. A message that former Labour Home Secretary, Alan Johnson, delivered as well.
Ed Miliband himself has now formally ruled out a Coalition with the SNP but other, less formal, arrangements could still be on the table.
The concern is that the SNP would be disruptive, whatever their role. That they would be looking out for their interests and of Scotland, not those of the whole of the UK.
That they would not follow the Westminster rules. A fear compounded by the likely presence of Alex Salmond in the House of Commons.
This comes down to the attitude of the SNP in Westminster.
They have already said they will vote on English matters which is a historic change. They are also being open about Trident and are not ruling out another go at independence.
So there is little to reassure Labour about the benefits of working with the SNP in any capacity let alone the now ruled-out formal Coalition.
Cities across the North of England could also react badly. Many of them are, and look continued to be, Labour strongholds.
But if they see Scotland doing well in a ‘government relationship’ potentially at their expense then there will be a backlash.
The Scottish Government has already attracted jobs from London by offering subsidies to firms to relocate roles.
The same could happen to roles from across other parts of England as well. The more devolutionary approach allows Scotland more powers that others will want to replicate.
Labour’s problem has often been said to be its ‘Southern Discomfort’, its inability to win seats in the South of England.
Blair managed this consistently but outside of London a breakthrough this time looks less likely. Combined with the possible result in Scotland, this would leave Labour as the party of the Midlands, North and Wales – hardly a national party.
If the Conservatives are returned to office then they are committed to a referendum on Europe. This assumes a ‘UK-wide’ negotiation but it is far from clear that all parts of the UK have the same wants or needs from Europe. The potential tensions are obvious.
A relationship between Labour and the SNP, however informal, could cause huge ructions. It could be as disturbing for Labour supporters as much as others.
The ultimate irony is that whilst Labour helped keep the Union together, no-one, on either side of the border, is thanking them for it.