WASHINGTON (Reuters) - The U.S. Justice Department said on Tuesday it had charged the chairman of the North Carolina Republican Party, Robert “Robin” Hayes, and a major political donor in a corruption scheme that targeted a state official.

FILE PHOTO: Chairman of the North Carolina Republican Party and former congressman Robin Hayes is seen in Hillsborough, North Carolina, U.S. October 17, 2016. REUTERS/Chris Keane

According to an indictment unsealed on Tuesday, Hayes worked with business executive Greg Lindberg to bribe state insurance commissioner Mike Causey. Causey reported the effort to law enforcement officials and cooperated in the investigation, authorities say.

The two men, along with insurance executives John Gray, 68, and John Palermo, 63, were charged with bribery and conspiracy to commit honest services wire fraud. Hayes is also charged with lying to the Federal Bureau of Investigation.

All four men pleaded not guilty.

Lawyers for Hayes and Lindberg said their clients looked forward to clearing their names in court. Lawyers for Gray and Palermo did not immediately respond to a request for comment.

According to the indictment, the four men promised to spend millions of dollars on Causey’s re-election if he would

remove an insurance regulator that oversaw companies under Lindberg’s control.

They said they would set up independent campaign committees that would spend $1.5 million on Causey’s re-election bid and funnel another $250,000 through the state Republican party.

Hayes encouraged the others to transfer the money in smaller amounts to avoid detection, the indictment said. “My concern, any large amount like that’s gonna draw attention,” he said, according to the charges.

Lindberg is the founder and chairman of investment company Eli Global and the owner of Global Bankers Insurance Group, which controls several insurance companies. Neither company was charged, and Global Bankers said it was cooperating with the investigation.

Lindberg is the state’s biggest political donor in recent years, with total contributions of more than $5 million, mostly to Republicans, according to news site WRAL.

Hayes served in the U.S. Congress from 1999 to 2009. He led the state party between 2011 and 2013, when it won a dominant majority in the state legislature, and again since 2016. He announced yesterday that he would step down from the position.

Lindberg and Gray also enlisted another public official, who made several calls to Causey on their behalf after they contributed $150,000 to a political committee supporting his candidacy, according to the indictment.

That official, identified by Politico as U.S. Republican Representative Mark Walker, was not charged. A spokesman for Walker said he had committed no wrongdoing and had assisted the investigation.

The North Carolina Republican Party said it has been cooperating with the probe for several months.

The party has suffered a series of setbacks after several years in which it controlled the state government, pushing through spending cuts, voting restrictions, and other conservative policies.

An absentee ballot fraud scheme run by a party operative has forced the rerun of a 2018 U.S. congressional election, and a federal court ruled last year that state Republicans illegally drew U.S. congressional districts to benefit their party.

Democrat Roy Cooper was elected as governor in 2016, breaking the Republican grip on state politics, and Democrats made significant gains in state assembly elections last year.