News about a purported affair between him and a top aide broke wide open more than a year ago, including the release of a tape in which Bentley talked lovingly about putting his hands on her breasts.
Nevertheless, Bentley spent months denying any wrongdoing or even having engaged in an affair.
"All the logic would have said he would have resigned long ago," says Wayne Flynt, a retired historian at Auburn University.
Instead, the Republican governor waited well past his political sell-by date. He not only resigned but also pleaded guilty to two campaign finance violations.
Bentley is far from the first politician who refused to step aside long after political logic seemed to dictate that he should have. There's a kind of hubris that can consume officeholders, convincing them that they're being judged unfairly or at least that they have the personal wherewithal and standing to survive a scandal.
"It's the kind of delusion that comes with power," says Bill Britt, editor-in-chief of the online news site Alabama Political Reporter. "One of the things we learned about Gov. Bentley over the last year is that he's like so many politicos in general who come to believe that they are not vulnerable or not subject to the same rules that the rest of us are."
Unless there's an indictment -- and sometimes not even then -- politicians sometimes decide they can tough out the storm. They may refuse to resign on the advice of counsel because their resignation itself can be a useful bargaining chip with prosecutors. In Bentley's case, his immediate resignation was part of his plea agreement. He also agreed never to seek public office again.
Bentley received a suspended sentence for converting campaign funds for personal use and for failing to have reported a campaign donation. He'll repay $8,912 worth of legal fees that were paid out of his campaign account. The remainder of his campaign fund, about $25,000, will be handed over to the state. Bentley will also be on probation for a year and perform 100 hours of community service as a physician.
The governor had long spurned calls to step down. Successful politicians aren't quitters. They've worked hard to achieve their positions and won't give them up lightly -- especially if members of their own party won't give them a shove.
"In states where one party is dominant [like Alabama], it's easier for politicians to try to ride out a scandal," says John Marion, executive director of Common Cause in Rhode Island. "The politician's party doesn't have an incentive to toss them overboard."
In southern states, where governors tend to have less power, there's even less incentive for the party to force out a weakened governor who can either be easily manipulated or, at best, serve as a caretaker.
That's one reason Bentley was able to last so long: Members of his own party didn't particularly want him to go. Money trails led from major party donors into the hands of Bentley's mistress and her husband, making a serious investigation potentially embarrassing for many. Also, a number of Republicans have been hoping to succeed the term-limited Bentley next year. There was little appetite among them to see Lt. Gov. Kay Ivey establish herself as the incumbent governor.
"A lot of Republicans are terrified [that] if Kay Ivey is able to have two years of competent government, she is going to have the inside track," says Flynt. "They would rather have the humiliation and scandal of Bentley, rather than Ivey being able to strengthen her role."
Similarly, Mark Sanford served out his term as governor of South Carolina more than a year after his extramarital affair had dominated national news in 2009. Andre Bauer, the lieutenant governor serving under him, came with his own baggage, including a number of traffic violations and an insensitive remark comparing poor people who receive public benefits to feeding stray animals.
"In Sanford's case, by the time they figured out how to replace him, his term would have ended," says David Woodard, a GOP consultant at Clemson University.
But over the past few days, the political and legal tides finally turned overwhelmingly against Bentley, and reluctant Republicans have had no choice but to break with the governor.
Last week, the state ethics commission found probable cause that Bentley committed multiple felonies in using state resources to cover up the affair. Separately, an investigator hired by the state House Judiciary Committee released a scathing report filled with excruciating detail about the governor's affair and his efforts to hide it. Impeachment proceedings got underway Monday.
"You would have thought the humiliation would have led him to say, 'I've done terrible things, I'm out of here,'" says Flynt. "That's the logic of the evangelical tradition from which he comes."
Yet as late as Friday, Bentley insisted he was the innocent victim of political enemies who sought to smear his name.
"Ultimately, there are two ways these things tend to end," says Marion, the Common Cause official. "One is that law enforcement pressure becomes so great that they have to resign or the party tosses them aside."
The dam finally broke. Too much evidence had entered the public sphere. One by one, the top legislative leaders and the state party itself stated publicly that Bentley had to go.
The end of the Bentley saga comes at the end of a particularly troubling year for Alabama and its Republican Party. In June, state House Speaker Mike Hubbard was convicted of felony ethics charges. In September, state Supreme Court Chief Justice Roy Moore was suspended for the remainder of his term for violating judicial ethics.
After more than a century out of power in the legislature, Republicans took control of all the political branches of Alabama state government in 2010. Now, the GOP, which forced the Democratic Party from power in large part through accusations of corruption, has to get its own house in order, after its own three most powerful members have all been forced from office.
"All the fighting will be within the Republican Party," says Flynt. "It's going to be a bloodletting from here on out. The next governor's race could well be about personal morality and making Alabama great again."