Georgia's powerful House speaker resigned Thursday after a suicide attempt and allegations by his ex-wife of an affair with a lobbyist.

Glenn Richardson, the state's first GOP speaker since Reconstruction, had won sympathy from even his political enemies when he revealed last month that he attempted suicide by swallowing sleeping pills. But then his ex-wife went on TV and accused him of having "a full-out affair" with a lobbyist while they were still married.

Richardson did not address that allegation in a brief statement issued through the House communications office in which he said he will leave both his position as speaker and his House seat on Jan. 1. He did mention his recent admission, made in the wake of his suicide attempt, that he has grappled with depression.

"I fear that the media attention of this week has deflected this message and done harm to many people who suffer from this condition," he said in the statement.

House Republican lawmakers received the news from an emotional Richardson during a conference call just before the statement was released.

"It was very painful for those of us on the listening end," state Rep. David Ralston said.

The 49-year-old Richardson, once thought to be a serious contender for governor, had gone right back to shaking hands at chicken-and-grits fundraisers after trying to kill himself. But he had been silent since his ex-wife claimed this week that he slept with a lobbyist pushing a $300 million pipeline bill he was co-sponsoring.

It has been a dizzying fall for one of Georgia's most powerful political figures. Sheriff's deputies found him Nov. 8, slumped semiconscious on the edge of the bathtub at his west Georgia home after he called his mother to say he had swallowed pills. A suicide note and a silver .357 Magnum were on the counter next to him. The contents of the note have not been released.

Secretary of State Karen Handel, a leading GOP candidate for governor in 2010, called Richardson's personal turmoil "heartbreaking" but said meetings at the state Capitol were grinding to a halt because he was missing in action amid the worst state budget crunch in the state history.

She and the Georgia Christian Coalition were among those who had called Thursday for Richardson to resign.

Once Richardson steps down, House Speaker Pro Tem Mark Burkhalter will become interim speaker, and the Republican caucus will have 120 days to elect a permanent replacement.

University of Georgia political science professor Charles Bullock said Richardson is known for comebacks, but the latest round of news may have finally damaged him beyond repair.