When it comes to S.& P., he doesn’t utter the word “regrets”  which S.& P. bigwigs tend to volunteer these days. In two hours of interviews in his office one recent afternoon, about the closest that he will come to suggesting that anything went haywire at S.& P. is this: “Assumptions were made and with respect to a portion of securitized ratings, the assumptions didn’t work.”

Sitting behind a huge desk in a corner office, dressed in a light blue Oxford shirt and a blue tie, he seems most comfortable discussing the finer points of law. Even now, in the senior-discount stage of his life, he gives the impression of a man fit enough to put you in a headlock, though he also seems too well mannered for fisticuffs. He answers questions deliberately, like one accustomed to having his words read back in a transcript. As he speaks, he slowly moves his coffee cup from a spot on his desk to a perch on a small stack of Post-it notes, then back to his desk, then back to the Post-its, over and over.

Mr. Abrams has worked for a mix of corporate clients that has included A.I.G. (before its near collapse), Reynolds Tobacco and, for about 20 years, McGraw-Hill, which owns S.& P. But media cases have made him the only First Amendment lawyer whom anyone outside the legal field can name. (He is representing a New York Times reporter who was called before a grand jury, but he’s no longer the paper’s go-to counsel, he says, because his price is too high.)

He became nationally known in 1971, at the age of 34, after he beat back the Nixon administration when it tried to block The Times’s series about a lengthy, secret account of the Vietnam War that had been drafted by the Pentagon. The Pentagon Papers case, as it was known, arrived at a moment in history when the rights of journalists  to protect sources, to publish classified documents, and so on  were flimsy at best, and by helping to make those rights robust, he became a media darling.

He would go on to defend clients like the Brooklyn Museum, which Rudolph W. Giuliani, then the mayor of New York, tried to shut down in 1999 because he found a piece of art in it offensive. Such fights have given Mr. Abrams the aura of a public-interest lawyer at large, an eminence who knows how to use the Constitution to deflect bullies.

There are legends in any field who coast on the fumes of early victories, but Mr. Abrams isn’t one of them, say law professors and fellow lawyers. He is still known for his don’t-give-an-inch approach to advocacy. In the rating agency field, that has earned him some critics.

“In my view, he hasn’t done the industry much good because his tactics have been too aggressive,” says Jerome S. Fons, a former Moody’s managing director. Mr. Fons has an example in mind: in 2004, the S.E.C. proposed a voluntary regulatory framework for the rating agencies. It never got much past the conceptual phase, and whatever it might have ultimately looked like, there’s little reason to think it would have defused the planet-rattling bomb that rating agencies were helping to ignite in 2004. But Mr. Fons says he thinks that at minimum, the framework could have “raised some red flags earlier,” and if that had happened, who knows?