Democratic presidential candidate Tom Steyer came under fire from his fellow 2020 hopefuls Thursday after it emerged that a top aide in Iowa had offered campaign contributions to local politicians in exchange for an endorsement.

Sen. Cory Booker, D-N.J., tweeted "This ain't it," a meme often used to push back against bad hot takes online, in response to the revelations.

Montana Gov. Steve Bullock was more critical of Steyer's team's behavior.

"First he buys his way onto the debate stage and now Tom Steyer’s trying to buy endorsements. These repeated efforts to undermine our democratic process are unacceptable,” Bullock said. “Tom Steyer’s campaign is built on writing the biggest checks, not on building genuine grassroots support – and proves why it’s so important to get Big Money out of our elections.”

The move from Pat Murphy, a former state House speaker and top adviser for Steyer in Iowa, was reported by the Associated Press. The AP said that there was no evidence that any Iowans accepted the offer, but such payments could have violated campaign finance laws if not disclosed.

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Steyer's campaign sought to defend itself by saying the candidate has not and will not contribute money to candidates in Iowa.

“Tom has not made any individual contributions to candidates in Iowa this year, and he will not be making any contributions. The endorsements he receives are earned because of Tom’s campaign message, his decade-long work taking on big corporations who put profits over people, and his work registering and organizing voters across the country to support progressive causes," Steyer's campaign said in a statement.

"Our campaign policy is clear that we will not engage in this kind of activity, and anyone who does is not speaking for the campaign or does not know our policy," it said.

Murphy, meanwhile, apologized for his actions.

"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," he said. "I joined the campaign because I believe Tom is the best candidate to take on Donald Trump and that he shares Iowa’s values."

But the proposals quickly led to criticism. Tom Courtney, a former Democratic state senator from southeastern Iowa who's running for reelection to his old seat, told the agency that the offer "left a bad taste in my mouth" although he didn't name Murphy as the aide who made the offer.

Courtney described his interaction with Steyer's campaign to The Associated Press.

"Tom, I know you're running for Senate. I'm working for Tom Steyer," Courtney recalled hearing from the aide. "Now you know how this works. ...He said, `you help them, and they'll help you."'

"I said, `it wouldn't matter if you're talking monetary, there's no amount,"' Courtney continued. "I don't do that kind of thing."

The overtures do not appear to have made much of a difference for Steyer. Aside from Murphy's support, Steyer has received the endorsement of just one Iowan since entering the race in July -- former state Rep. Roger Thomas.

Thomas did not respond to phone calls from The Associated Press, but in a statement provided by the campaign, he said that he endorsed Steyer "because he's the outsider who can deliver for Iowans on the issues that matter most: getting corporate corruption out of our politics and putting forth a rural agenda that revitalizes communities across Iowa."

Thomas' endorsement was issued in October after the close of the most recent campaign finance reporting period, which ended Sept. 30. The disclosure Steyer filed offers no indication that he directly gave Thomas any money.

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A trio of former Ron Paul aides faced legal trouble in 2016 over similar issues during the 2012 Iowa Republican caucus campaign.

Campaign chairman Jesse Benton, campaign manager John Tate and deputy campaign manager Dimitri Kesari were convicted in 2016 of charges related to arranging and concealing payments for then-Iowa state Sen. Kent Sorenson, who switched his support from then-Rep. Michele Bachmann to Paul just six days before the Iowa caucuses. Sorenson served 15 months in jail for his role in the scheme.

It's unclear whether Murphy could face a similar legal complaint, but the issue could revive scrutiny of how Steyer is deploying his financial resources. The billionaire businessman built his fortune in banking and investment management before turning to politics, and though he's never held public office he invested tens of millions of dollars in political activism and electoral politics before launching his presidential bid this year. Prior to his presidential run, Steyer's most recent focus was a multi-million-dollar, pro-impeachment campaign, and as the U.S. House takes up the issue, he's argued he's put it on the national agenda.

Steyer has largely self-funded his presidential campaign, spending $47.6 million of his own money in the first three months since launching his bid, much of that on online fundraising and advertising. Steyer qualified for the November debate, but he remains at the back of the pack in early-state and national polls.

Fox News' Adam Shaw, Alexandra Rego and The Associated Press contributed to this report.

