Kay Ivey has been sworn in as Alabama's new governor after Robert Bentley resigned and pleaded guilty to two misdemeanor charges that arose from an investigation into his alleged affair.

Ivey, who had been lieutenant governor, took the oath of office Monday at a ceremony at the Alabama Capitol. Bentley pleaded guilty to two misdemeanor campaign finance law violations.

Ivey called it a dark day in Alabama politics and a day of opportunity. She promised her administration will be open and honest.

She is Alabama's second female governor.

Bentley resigned Monday amid possible criminal probes and impeachment hearings following the release of a report detailing Bentley's alleged misuse of state resources to pursue and later cover up an affair.

The attorney general's office announced the resignation Monday with a plea deal.

In a Monday evening speech, the governor said he'd not always made the right choices.

"Though I sometimes failed, I've always tried to live up to the high expectations the people placed on the (person) who holds this esteemed office," he said at the Capitol.

The stunning resignation came after Bentley pleaded guilty to two misdemeanor violations of campaign finance law.

Bentley's voice began choking with emotion as he addressed reporters at the Alabama Capitol. He said he always tried to live up to the high expectations placed on the person who holds the esteemed office. He apologized for mistakes.

Alabama's Ethics Commission last week found probable cause that Bentley violated state ethics laws with his handling of an alleged affair and referred the case to prosecutors.

Bentley's governorship became increasingly overshadowed by allegations he pursued an affair with former staffer Rebekah Caldwell Mason and attempted to use state resources to pursue it, and state law enforcement to cover it up. The allegation led Monday to an unprecedented impeachment hearing into the governor.

"Robert Bentley, governor of Alabama, directed law enforcement to advance his personal interests over those of the state," Jack Sharman, special counsel for the House Judiciary Committee, told representatives Monday afternoon. "In timelines characterized by increasingly desperate conduct, he subjected honest career law enforcement to tasks to protect his reputation, both political and personal."

An impeachment report released Friday accused Bentley of becoming obsessed with recovering recordings of conversations between him and Mason made by Dianne Bentley, who divorced the governor in 2015 after 50 years of marriage. According to the report, Bentley threatened staffers who knew or who he thought knew about the affair, and sent law enforcement to recover the recordings or question those he thought might know about them. Bentley is also accused of using a security member to try to break up with Mason on at least two occasions.

The report also alleges Bentley brought Mason with him in state vehicles and aircraft, at times overriding his security detail to do so. Sharman said he only received pre-edited flight logs upon request.

The impeachment report was one of a host of struggles faced by the governor. Two days prior, the Alabama Ethics Commission found probable cause that the governor violated ethics and campaign finance laws, and forwarded their findings to Montgomery County District Attorney Daryl Bailey for further prosecution. Bailey sent those findings Monday to Ellen Brooks, serving as acting attorney general in a probe that office is conducting into Bentley's conduct. Alabama Attorney General Steve Marshall, appointed by the governor in February, recused himself from the investigation shortly afterward.

Legislative leaders had been carefully noncommittal about impeachment since House members first pushed a resolution through last year, but the Ethics Commission report, combined with the impeachment proceeding, pushed Senate President Pro Tem Del Marsh, R-Anniston and House Speaker Mac McCutcheon, R-Monrovia, both called for Bentley's resignation last week. Bentley called an impromptu presser on Friday to say he would not.

“Once again, let me say I do not plan to resign,” the governor said Friday. “I have done nothing illegal. If the people want to know (whether) I misused state resources, the answer is simply no, I have not.”

It was the first impeachment considered by the Alabama House of Representatives since 1915, and the first ever directed at an Alabama governor.