Florida Representative Trey Radel resigned from Congress on Monday. Radel pleaded guilty to a cocaine possession misdemeanor charge late last year. After a stint in rehab, the representative originally indicated in December that he planned to stay in office: "I love what I do," he said in a press conference, "and I'm going to return to what I do." Radel's chief of staff Dave Natonski confirmed the news to the HillHis resignation is effective at 6:30 p.m. on Monday. 

Shortly after the news broke, Radel sent a letter to Speaker of the House John Boehner: "Some of my struggles had serious consequences," Radel wrote of his drug conviction, adding, "While I have dealt with those issues on a personal level, it is my belief that professionally I cannot fully and effectively serve as a United States Representative." 

Radel originally seemed to want to put the incident behind him and keep working in Congress. But that's easier said than done. For instance, Radel was the subject of an ongoing House Ethics Committee investigation into whether his illegal drug possession violated House rules. Since the conviction, Radel has faced several calls from Republican leaders — and from the Republican Party of Florida — to resign. 

Earlier in January, the congressman wrote the following op-ed in the Island Reporter as part of what was apparently a campaign to win back the trust of his constituents: 

As your servant in Congress, my voting record is indisputable when it comes to fighting for you and your family. Your health care, our economy and our environment have always been my top priorities. I have fostered solid relationships with both parties to find solutions and get things done. I have been and will continue to be one of the most accessible members of Congress, personally taking your calls and emails, and, of course, visiting you in person.

Radel returned to the House in January after a leave of absence to undergo treatment. In October, the congressman purchased cocaine from an undercover law enforcement official. He was later sentenced to one year of probation

As the Washington Post notes, Radel was already facing an August primary challenge in the heavily conservative district: Former Republican state Rep. Paige Kreegel had filed paperwork to run against Radel. There were also rumors that former Republican Rep. Connie Mack might run to reclaim his old seat. Radel will submit his resignation to Speaker of the House John Boehner some time on Monday. 

Here's the full letter, via Luke Johnson: 

This story has been updated with new information.