The 2015 UK elections were decided by the issues surrounding Scotland. End of story.
It wasn't because Labour wasn't left enough - if that was true, why didn't people turn out in droves for the Greens in English and Welsh constituencies? (It's not as if the Greens didn't have a fighting chance to grow as much in the rest of the UK as the SNP did in Scotland. UK political campaigns aren't as lengthy or money-drenched as are US ones; that's a big reason why the Greens have a presence in Parliament whereas there are no Greens on Capitol Hill. Another is because of the very nature of the parliamentary system as compared to ours. Yet another is that the UK Greens are better organized than their cousins across the pond. But that's another story.)
Labour's leaders were caught in a trap, a trap that was sprung last year: Alienate their Scottish constituencies by backing a "no" vote on Scottish independence, or sit back and watch as the Tories successfully tarred them as the party that destroyed the UK.
The worst-case scenario unfolded, as both of these things happened. Follow me past the cartouche for more.
A good synopsis can be found in The Guardian:
Miliband’s team believe that many voters south of the border were simply frightened away. Relentless Tory “lies” claiming a Miliband government would not only wreck the economy but would be in the pocket of the SNP had paid off spectacularly. The “soft” element of the Labour vote – those who liked Miliband but were not entirely convinced – was susceptible, the former leader’s inner circle now thinks, to the fears that Crosby’s campaign instilled in them. They also believe that many people were embarrassed to tell pollsters that they were going to vote Tory. “They were bullied by the Tories but they could not admit it,” said a source close to Miliband. “We believed we were doing well, because we could not see this going on. The Tories’ tactic worked.”
Ukip voters returned to the Tories more than they did to Labour. Murphy said that north and south of the border Labour was caught in a perfect storm. “We were hit by two nationalisms,” he said. “A Scottish nationalism reassuring people that they could vote SNP and get Labour. And an English nationalism stoked up by Cameron: warning vote Labour and get SNP.”
The Lib Dems seem to have been swept away by similar forces as voters bought into the Tory message that it was a choice between the chaos of Labour with the SNP or stability with the Tories. Labour officials concede that maybe they should have tried to play as hard and as rough as the Tories did, but simply weren’t able. “We tried negative campaigning in the last two weeks over benefit cuts and the NHS, but we were not very good at it. Our heart wasn’t really in it.”
So what's going to happen now?
Well, the Scottish National Party is now pushing for full fiscal autonomy from the UK, and Cameron and the Tories may well give it to them, most likely on the idea that it would wreck the Scottish welfare state and save the rUK a lot of money. (That's why Daniel Hannan, a Conservative Member in the European Parliament, is hoping Cameron does it.) It would tie beautifully, from Cameron's perspective, with his "English Votes for English Laws" campaign, a scheme wherein Scottish MPs, now that their own parliament in Holyrood has been given taxing powers, would no longer be able to vote on taxation bills affecting the rest of the UK.
In a freakish way, it would almost seem that the leaders of the SNP are re-enacting a bit of Scottish history. Like the SNP leaders of today pushing their schemes, the Scots promoting the Darien Scheme thought they were doing something that would make their nation freer and stronger; instead, it led to them all but begging the English to take them in under the Act of Union.
But as I've found when dealing with antivaccine activists, you can't reason people out of positions they were never reasoned into.
Update at 8:56 pm PDT: The "Labour voters stayed home out of disgust with Tory-Lite Labour policies" doesn't wash as 1) Turnout was higher this year than in 2010 (it's been steadily rising since bottoming out in 2001, in fact) and 2) Labour's share of the vote actually increased from 2010.