Last week, the Alabama Ethics Commission cited evidence that Bentley broke state ethics and campaign laws and referred the matter to prosecutors who could have sought felony charges tougher than the misdemeanors to which Bentley pleaded guilty.
Although it lifted the restraining order, the court asked for briefs to be submitted by Monday afternoon.
"I have decided it is time for me to step down as Alabama governor", said Bentley at a news conference in the state capital of Montgomery, adding that his service "was a calling that God placed on my life". So there were also questions about state resources and campaign funds being used to further the alleged affair.
Lt. Gov. Kay Ivey has assumed the role of governor.
One misdemeanor charge against Bentley stemmed from a $50,000 loan he made to his campaign in November that investigators said he failed to report until January.
Voters in the deeply conservative state re-elected Moore as chief justice in 2012, but a state judicial panel suspended him from the post a year ago over an order he issued opposing same-sex marriage. Ivey, 72, will be Alabama's second female governor, following Democrat Lurleen Wallace, according to the Huffington Post.
"[She] noticed not only the changes in her husband's wardrobe but also the changes in his demeanor", Zengerle said.
The scandal broke last spring when the state's top police officer - fired by Bentley - provided the news organization AL.com with salacious details of the secret romance. "Robert Bentley could not handle the power".
In texts between the governor and Mrs Mason in 2010, Mr Bentley replied: "You are wonderful my sweet love".
A former staffer told the Alabama House Judiciary Committee that the governor had insisted to members of his administration: "What happens in the governor's office stays in the governor's office". "Corruption was spotted, recognized and dealt with. even though it was slower and little more painful than we had anticipated". Dianne Bentley had secretly recorded her husband by leaving her phone on while she went for a walk.
Bentley had vowed as recently as Friday not to resign, saying he had done nothing illegal. The Republican governor alienated many of his fellow Republicans in the legislature - ironically (in light of subsequent events), for morally sound reasons.
Former Alabama Republican Party Chairman Marty Connors noted that it was the GOP attorney general's office opened the investigation against Hubbard and it was Republican lawmakers who threatened Bentley with impeachment.
But such moral high ground was impossible to hold as Bentley was forced to reveal his own gross hypocrisy in having cultivated the political image of a devoted faith-and-family man and, worse, having violated the law to protect it. "My district has suffered the last two years because of my battle with Gov. Bentley", he said. He agreed to never run for office again and serve one year probation.