Jesse Benton, the campaign manager for Sen. Mitch McConnell, R-Ky., resigned Friday amid deepening questions over his involvement in a payola scandal by the 2012 presidential campaign he helped run.

On Wednesday, former Iowa state Sen. Kent Sorenson pleaded guilty to switching his support for Rep. Michele Bachmann to endorse former Rep. Ron Paul during the Iowa Caucuses in exchange for $73,000, which was paid to Sorenson by Paul's campaign through back channels. Benton was Paul's campaign chairman at the time, but has not been charged with a crime.

"Recently, there have been inaccurate press accounts and unsubstantiated media rumors about me and my role in past campaigns that are politically motivated, unfair and, most importantly, untrue," Benton said in a statement Friday distributed by McConnell's campaign. "I hope those who know me recognize that I strive to be a man of integrity."

"However," Benton added of the reports, "what is most troubling to me is that they risk unfairly undermining and becoming a distraction to this reelection campaign."

McConnell faces a competitive challenge from Democrat Alison Lundergan Grimes. In his statement, Benton said there is "no more important cause" than electing McConnell to another term in the Senate.

"I believe this deep in my bones, and I would never allow anything or anyone to get in the way," Benton said. "That includes myself."

Benton's resignation promises to become an issue in the campaign, in particular as the investigation in Iowa further unfolds.

"Sen. McConnell owes the people of Kentucky a full account of what he knew and when he knew it," said Charly Norton, a spokeswoman for Grimes.

The dramatic ending to Benton's tenure with McConnell comes after an unusual arranged political marriage between the campaign operative and the candidate.

After working on Ron Paul's presidential campaign, Benton, who married into the Paul family, steered Sen. Rand Paul to a surprising victory in a competitive Republican primary. Mr. McConnell took notice and hired Benton for his own re-election — but Benton later admitted during a recorded phone conversation that he was “sort of holding my nose for two years” working for McConnell, until he could return to Rand Paul's fold.

Benton's resignation could have serious implications should Rand Paul decide to run for president. After McConnell's re-election, Benton was expected to be a cornerstone of Paul's 2016 campaign operation.