4 ideas
Jeanne-Antoinette Poisson, a financier's daughter, became Louis XV's official mistress in 1745. Around 1750 their sexual relationship ended, yet she stayed at Versailles until her death in 1764. In those years she steered ministerial appointments like those of Bernis and Choiseul, backed the 1756 alliance with Austria, and in 1756 was made a lady-in-waiting to the Queen, all without ever holding any government office.
Pompadour survived the end of the sexual relationship because she had already turned her value to the king into something else. She had become his companion, his entertainer against chronic boredom, his confidante and his political intermediary. Influence that rests on one perishable asset lasts only if the holder moves it onto functions the patron cannot easily replace before that asset fades.
Ministers, artists and courtiers learned that going through her was the working route to royal decisions. Control over access and the flow of favours can create obligations that behave like formal authority.
Because Pompadour's influence was visible but had no official standing, she absorbed public hostility for unpopular outcomes such as the Seven Years' War. Pamphlets (the 'poissonnades') attacked her low birth, while her position depended entirely on the continued goodwill of a single man. Looking at informal power this way shows its hidden cost: the holder is blamed as if accountable yet has no institutional shield, and the power ends when the patron withdraws or dies.