Stable majorities rely on a country's political and media elite to behave somewhat responsibly. In the UK, the EU became a welcome punching bag that every negative domestic feeling and development could be pinned on. That's a quick way to destroy even the most positive of associations and is at the root of the Brexit disaster (and the anti-EU sentiment in other countries like Germany).

True, of course. But how else would you gauge the stability of a majority? I would have thought the size of it is the main proxy.