For the last 17 months, Eric T. Schneiderman, the attorney general of New York, had held himself up as the anti-Trump: a one-man legal wrecking ball, taking on the president and his agenda in both the courts and the court of public opinion.

His sudden and spectacular downfall — Mr. Schneiderman announced his resignation hours after four women emerged to describe in detail how he had physically assaulted them — has raised questions of whether a powerful office at the heart of the Democratic legal resistance could be sidelined and besmirched by scandal.

Some have even held up Mr. Schneiderman as a potential backstop to prosecute crimes should President Trump choose to pardon his associates in the continuing special counsel investigation led by Robert S. Mueller III. The president’s vast federal pardoning powers do not apply to violation of state laws.

“If you imagine a next attorney general in New York who is not as interested in being the big anti-Trump figure, that’s a potentially significant difference,” said Benjamin Wittes, a Brookings Institution senior fellow and the editor in chief of LawFare.