Expression to describe self-inflicted fall from a position of strength

Question

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.

Answer 1

This answer is in no way a comment on Cameron, about whom I know next to nothing.

Hubris, Wikipedia, Hubris

Hubris (/ˈhjuːbrɪs/, also hybris, from ancient Greek ὕβρις) describes a personality quality of extreme or foolish pride or dangerous over-confidence.[1] In its ancient Greek context, it typically describes behavior that defies the norms of behavior or challenges the gods, and which in turn brings about the downfall, or nemesis, of the perpetrator of hubris.

See also hubris, The Free Dictionary

An ancient Greek word meaning pride or arrogance, used particularly to mean the kind of excessive pride or conceit that often brings about someone’s downfall

Example from TFD:

Ego check; why executive hubris is wrecking companies and careers and how to avoid the trap

Answer 2

Political Suicide (wikipedia)

Political suicide is a concept by which a politician or political party loses widespread support and confidence from the voting public by proposing actions that are seen as unfavorable or that might threaten the status quo. A politician who is seen as having committed political suicide might be forced to resign from either external public pressure (such as the threat of civil unrest) or internal pressure from superiors or colleagues.

Answer 3

In the US, an expression heard of in sports is "taking a dive" for knowingly losing when one could win, or "taking one for the team" when there is a sense of self-sacrifice. Whether they would carry over into the political realm seems iffy.