Kent Sorenson, the Iowa state senator linked to an ongoing ethics investigation of former presidential candidate Rep. Michele Bachmann (R-MN), resigned from office Wednesday, after an investigation by Iowa’s Senate Ethics committee found “probable cause” that Sorenson violated state ethics rules by taking payments from the Bachmann campaign and that his denials of doing so constituted felonious misconduct in office.

Iowa Senate ethics rules prohibit a state senator from being paid as an employee by a presidential campaign. The idea is to prevent campaigns from essentially bribing legislators for their endorsements by hiring them as “consultants.” According to an ethics complaint filed by former Bachmann staffer Peter Waldron (who also wrote a tell-all exposé of the campaign, the campaign funneled money to C&M Strategies, a firm owned by Bachmann’s longtime direct-mail consultant, Guy Short, to pay Sorenson an illicit six-figure salary. This has also sparked separate federal allegations as to whether this action, if it occurred, violated federal campaign-finance law as well as congressional-ethics rules.

Sorenson told the Associated Press that his resignation was "absolutely not" an admission of wrongdoing. "I've spent money fighting this that I shouldn't have. I'm just not going to do that to my family anymore," he said.

Sorenson was also linked to another scandal during his tenure with the Bachmann campaign, which related to his alleged theft of a mailing list of conservative Christian homeschooling families. This provoked a civil lawsuit against Bachmann, which has since been settled. Mark Weinhardt, the independent counsel for the Senate Ethics Committee, said there were reasons to be “deeply suspicious” that Sorenson had stolen the list or was involved in a criminal conspiracy to steal the list.

A few days before the Iowa caucuses, Sorenson jumped ship to endorse Ron Paul. The special counsel found that Sorenson took a $25,000 check directly from the Paul campaign, which he did not cash. He also received $73,000 in wire transfers, which Weinhardt described as "deeply suspicious," although he said he was unable to connect them directly to Paul's campaign.

Waldron, who first made the allegations about payments, said the whole episode had been damaging to the state. “I am pleased to be vindicated but naturally regret that the Iowa first-in-the-nation caucus position has been soiled by the events uncovered by the special counsel,” he told The Daily Beast.

An investigation into Waldron’s complaint about the Bachmann campaign’s conduct with the Office of Congressional Ethics is still ongoing.

Sorenson’s resignation opens up a vacancy in his suburban–Des Moines state Senate seat and sets up a contentious special election in the perennial swing state of Iowa. Prior to Sorenson’s resignation, Democrats had only a one seat majority in state Senate, while Republicans control both the state House of Representatives and the governor’s mansion.