Mortimer Matz, a New York public relations impresario who was credited with introducing the raincoat as an essential fashion accessory so that recently arrested defendants could hide their handcuffs from photographers, and who co-founded a gluttonous annual hot dog eating contest to promote Nathan’s of Coney Island, died on Thursday at his home in Manhattan. He was 100.

The death was confirmed by his daughter Suzanne Matz.

Mr. Matz coupled street smarts, tabloid showmanship and the intellect of an Amherst English literature major to polish the profiles of politicians and other publicity seekers, as well as to advance the causes of corporate clients, protect the names of innocent victims of gossipmongers and salvage the reputations of the guilty.

He was not a conspicuous public presence. He had no swanky office suite and no fancy stationery. He was infrequently quoted by name.

He preferred, instead, to wield his image-making magic behind the scenes by feeding information to reporters, whose confidence he cultivated over decades through his uncommon candor.

His network of informants, combined with his native ingenuity and the equanimity of a former World War II bomber navigator, enabled him to transform potentially embarrassing adversities into small victories, and to elevate accused miscreants into Runyonesque rogues.

“I loved my background role as the go-to guy who knew where the bodies were buried (my clients buried some of them),” Mr. Matz told The Daily News in 2024, “and parlayed that knowledge as currency to help improve the image of the people I worked for by persuading reporters to give my clients the benefit of the doubt or, better yet in some cases, to disregard them altogether.”