Who is Nico Della Guardia from Presumed Innocent and what is their importance?

Nico "Delay" Della Guardia is the lawyer who wins an election early in the novel to become the county's prosecuting attorney. He earned his nickname early in his career, because he could never complete a brief on time. About forty years old and a trim man of dashing appearance, he is the consummate networker, especially with the media. When he plants news stories that undermine the prosecuting attorney, in hopes of elevating his own chances to assume that post, he is fired by the chief deputy, Rusty. He does not hold an outward grudge toward Rusty and instead projects a brassy sincerity that he applies to everyone. Nico is relentless and confident. He is not particularly smart but he is good-looking, dresses well, and knows how to glad hand. Rusty thinks of Nico as "a pygmy in his soul."