Labour and the Conservatives should learn this lesson from the SNP

In a significant return to two-party politics, Britain’s two largest parties are giant again. But it can only last for so long.

It’s the political equivalent of what goes up must come down. Political parties have periods of success, and in those moments at the top they feel invincible. Take the SNP for instance, following the Scottish independence referendum they must have felt like they were on top of the world when they stormed into Westminster with fifty-six out of a total of fifty-nine MPs.

Who would have thought that two years later, thanks to a radical Labour party and a proudly unionist Conservative party, that the SNP’s dominance would falter so dramatically?

One reason for this is that the SNP were a broad church. A movement that size cannot be anything other than that. Off the back of an independence vote, the 2015 SNP voters were united in that strong belief for independence. They also scooped up many voters fed up with austerity. Fast-forward two years, and the party probably suffered for two reasons. One, many voters were fed up with continued discussions about another referendum. Two, many of those seeking a radical, progressive alternative, who found it in the SNP in 2015, found it in Jeremy Corbyn this time around.

Broad churches can break when credible alternatives for parts of the alliance emerge.

Both Labour and the Conservatives achieved over 40% of the UK-wide vote in June’s election. Both siphoned off voters from other parties in an election that almost felt like a presidential battle between Theresa May and Jeremy Corbyn.

On top of that, both parties are continuing to hold commanding swathes of the vote in opinion polls, but so did the SNP.

What goes up, must come down.

The question now is, who will fall first?