When initially questioned by F.B.I. agents in May 2017 about the disclosure to the reporter, Mr. McCabe said he had not approved it and did not know who did. Other evidence contradicted his assertion. Then in late July, two investigators with the inspector general’s office interviewed Mr. McCabe about the disclosure to the newspaper. They determined he had not been truthful, saying he had essentially made the same false denial as he did previously in May, “except this time the false denial was made in an audio-recorded interview.”

The inspector general referred his findings to federal prosecutors in Washington in the spring of 2018 after concluding his investigation.

But what should have been a seemingly straightforward case with a limited number of witnesses and facts has dragged out amid internal deliberations. It has been under investigation for so long that the term expired for the grand jury hearing evidence. One of the lead prosecutors, Kamil Shields, was unhappy with the lengthy decision-making process and has since left the Justice Department for private practice. Ms. Shields declined to comment.

Another prosecutor, David Kent, also left the case recently. It is not clear why he departed but it would be an unusual move if prosecutors were indeed planning to charge Mr. McCabe.

Among the witnesses called before the grand jury was Lisa Page, who worked closely for Mr. McCabe at the F.B.I. as his special counsel and later gained notoriety for text messages she exchanged with another F.B.I. official disparaging Mr. Trump. Mr. McCabe had authorized Ms. Page to speak with the Wall Street Journal reporter, but he told investigators on two occasions that he did not remember doing so. He later corrected himself.

Ms. Page told the grand jury that Mr. McCabe had no motive to lie because he was authorized as the deputy F.B.I. director to share the information with the newspaper. Her assertion could be damaging for prosecutors, who would have to prove that Mr. McCabe knowingly and intentionally lied to investigators. A lawyer for Ms. Page declined to comment.

The inspector general said that Mr. McCabe’s decision to release the information to the newspaper was self-serving — “an attempt to make himself look good,” according to the office’s report — but Mr. McCabe has said it was justified and in the public’s interest. The inspector general said the disclosure effectively confirmed the existence of the Clinton Foundation investigation, which James B. Comey, then the F.B.I. director, had refused to do in July 2016 in congressional testimony.