Twelve months ago, Mr David Cameron — the British Prime Minister in government alliance with a smaller party — won a surprise outright victory in a general election. This put him in a position of considerable power. However he subsequently called a referendum on British Membership of the EU, campaigned for remaining in the EU, lost, and resigned. Is there an expression to describe squandering a position of such strength. “Shooting oneself in the foot” conveys the self-inflicted nature of his fall but does not convey the idea of squandering a strong position.
N.B. This is not a political question nor intended to invoke political discussion. There must be similar historical examples of this. I have stated what happened. I am looking for an expression to describe it.