Subpoenaed to testify under oath before a state legislative committee investigating the governor, the woman said that she went to Mr. Greitens’s home on his invitation one morning, where he suggested that they work out together; then he blindfolded her, taped her hands to pull-up rings and began kissing her. He then tore off her shirt, pulled down her pants and took a picture of her with his cellphone, she said.

But in mid-May, with a jury already being picked for a trial that was scheduled to begin in a matter of days, prosecutors suddenly dropped the invasion-of-privacy case against the governor. They said they had no choice but to drop the case because the prosecutor, Kimberly Gardner, was being called as a witness by Mr. Greitens’s defense team.

A week later, a St. Louis judge appointed a special prosecutor, Ms.s Baker, to consider whether to refile the charge.

Legal experts have said the case had other problems all along — not least that the prosecutors had not come up with the photo that was said to be at the center of the case, despite searches of the governor’s phone.

What else was Greitens facing?

The governor had also faced a second, unrelated felony charge. In April, Mr. Greitens was accused of illegally obtaining a donor list from a charity he founded and using it to raise money for his 2016 campaign. Ms. Gardner, the circuit attorney in St. Louis, charged him with one count of tampering with computer data; Mr. Greitens’s lawyer called the charge “absurd.” Shortly after the governor announced his resignation, Ms. Gardner said in a statement that she had “reached a fair and just resolution” of the charge against Mr. Greitens, and that details would be announced Wednesday.

Then there was the threat of impeachment in a State Capitol where both chambers are dominated by Republicans; lawmakers had convened a special session earlier this month.

In Missouri, leaders are subject to impeachment for a broad array of failings — “crime, misconduct, habitual drunkenness, willful neglect of duty, corruption in office, incompetency, or any offense involving moral turpitude or oppression in office.”