A top aide for Democratic presidential candidate Tom Steyer who offered campaign contributions to Iowa politicians in exchange for an endorsement of the 2020 hopeful has resigned, the campaign announced Friday.

"After the conclusion of an investigation alleging improper communications with elected officials in Iowa, Pat Murphy has offered his resignation from the campaign effective immediately," Steyer's campaign manager Heather Hargreaves said in a statement.

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The Associated Press reported Thursday that there was no evidence that any politicians accepted contributions from Murphy, a former state House speaker and top adviser to Steyer, but such payments could have violated campaign finance laws if they were accepted and not disclosed.

Murphy apologized for his actions on Thursday, saying: "As a former legislator, I know how tricky the endorsement process can be for folks in Iowa. It was never my intention to make my former colleagues uncomfortable, and I apologize for any miscommunication on my part. I joined the campaign because I believe Tom is the best candidate to take on Donald Trump and that he shares Iowa’s values."

Still, Steyer's campaign said that they "will not engage in this kind of activity, or any kind of communication that could be perceived as improper. Violation of this policy is not tolerated."

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Steyer, a billionaire hedge fund owner and progressive activist who entered the race this past summer, has struggled to gain traction. A Fox News poll of national Democratic primary voters published Sunday showed him with one percent support.

"The endorsements Tom receives are the sole result of his consistent efforts engaging communities, meeting them where they are, and earning their trust and respect with his unifying messages. The campaign will continue to seek them in Iowa and other parts of the country," Hargreaves said. "The campaign will continue to build on Tom's momentum in Iowa and across the country."

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Murphy's resignation comes just days after another Steyer aide resigned after it was discovered that he stole volunteer data from the campaign of rival candidate Sen. Kamala Harris, D-Calif.