The closest I can think of is the Profumo scandal in England some years back. I don't remember his position, but something important to the PM. His affair with a call girl (Mandie Rice Davies? those aging gray cells you know) was publicized and caused his resignation.
Maybe there's a parallel in ancient Rome. Tacitus imputed sexual perversions to Tiberius in order to blacken him. Petronius, ordered to commit suicide (the result of a palace intrigue), instead of composing verses flattering to the Emperor as one was expected to do before one's suicide, detailed Nero's sex life. That work has disappeared, leaving the Satyricon as the only extant work of Petronius.
On the whole, the subject's sex life was used in Roman times for character assassination but only in the third person:
My sex life is fascinating, you must be dying to hear it.
Your sex life alarms me, and I speak to you as a Dutch
uncle.
His (or her) sex life is disgusting. Yech.