The SNP's huge victory in the General Election saw some truly incredible swings. It made me wonder what would have happened if the SNP had been standing in England and Wales, too.
To find out, I first calculated the changes in each party's support in Scotland between 2010 and 2015. I measured this in terms of the electorate, so because the turnout went up, the figures don't add up to zero.
I also decided to calculate the changes separately for each incumbent party, because the swings weren't exactly the same (to be honest, the swings were actually more similar than I had expected, but they differences were still significant):
In Labour-held seats:
In LD-held seats:
In SNP-held seats:
In the Tory-held seat:
I then applied these changes to the 2010 results from England and Wales (treating Plaid Cymru as the equivalent of the SNP given they're sister parties), and the results are truly astonishing: Cons 309, SNP/PC 221, LD 34, Lab 7, others 2.
When we add these figures to the actual results from Scotland, the 2015 election results would have looked as follows for Great Britain: Cons 310, SNP/PC 277, LD 35, Lab 8, others 2. This means it would probably have been possible to form a minority SNP government with support from the other non-Tory parties.
(In case anybody is interested, the seven surviving Labour MPs would have been elected in these constituencies: Bootle, Ealing Southall, East Ham, Knowsley, Liverpool Walton, Liverpool West Derby and Mitcham & Morden.)
Of course the SNP wouldn't have achieved these results simply by standing in England, but it shows the potential for an English party that tries to emulate the SNP.