Powerful political adviser David Garth, 84, who spearheaded the creation of the modern political TV commercial and helped elect governors, senators, and mayors, died Monday at his home in Manhattan after a long illness, said longtime colleague George Arzt.

Mr. Garth never held office but was instrumental in shaping New York's government and political process. The mayors he helped elect - John Lindsay, Ed Koch, Rudy Giuliani, and Michael Bloomberg - served 38 of the last 45 years, and he helped Gov. Hugh Carey capture office in 1974.

Arzt said no one in his lifetime ever talked about Mr. Garth "without putting genius in front of his name."

"He's probably had more of an impact on the history of the city since the 1960s than any one person," Artz said. "There probably will never be anyone like him again."

Mr. Garth, who worked for Democrats and some moderate Republicans, was known for being fiercely competitive with a high success rate on Election Day. He was an outsized figure who was known for his salty language and became the basis for the political mastermind in The Candidate, the 1972 Robert Redford 1972 movie. - AP