A former Iowa state senator who was a key official in Rep. Michele Bachmann's 2012 presidential campaign pleaded guilty Wednesday to illicitly concealing payments he received to switch his support from Bachmann to then-Texas Rep. Ron Paul.

Former GOP state Sen. Kent Sorenson received thousands of dollars in "under the table payments," according to the Justice Department, to ditch Bachmann’s campaign, where he had served as Iowa chairman. He endorsed Paul instead.

The Department of Justice brought charges against him for allegedly lying to federal investigators about the money.

Sorenson’s support was seen as a key endorsement in the 2012 Iowa contest, which is the first-in-the-nation test for candidates seeking their party nomination.

Sorenson was named Bachmann's state campaign chairman in June 2011. But by the fall, Bachmann's momentum in the polls had stalled. Six days before the Iowa Republican caucuses, Sorenson announced his support for Paul.

In the plea agreement, Sorenson admitted concealing payments of $73,000 after secretly negotiating to switch his support. The payments came in monthly installments of roughly $8,000, according to DOJ.

The former lawmaker pleaded guilty to obstruction of justice and causing a campaign to falsely report expenditures. Sorenson could face up to 20 years in prison for obstruction of justice, and as many as five years on the second charge.

After Sorenson's switch in December 2011, Bachmann immediately claimed Sorsenson told her he was offered "a lot of money" by Paul's people.

Sorenson, though, denied the claim in a December 2011 interview with Fox News. He said he was "never offered a nickel."

"I did not accept any money from the Ron Paul campaign," he said.

Paul ended up placing third in the Iowa contest, with Bachmann far behind.

Sorenson, 42, resigned from the Iowa Senate a year ago. However, he has said his decision at the time was "absolutely not" an admission of wrongdoing.

His resignation came just hours after Mark Weinhardt, a special prosecutor asked to investigate whether Sorenson had broken Iowa Senate rules, released a report saying it was "manifestly clear" Sorenson negotiated payments in 2011 in exchange for his work as Bachmann's Iowa campaign chair.

Such payments violate the state Senate's rules that forbid any sitting lawmaker from being paid by a campaign while in office. The criminal complaint against Sorenson came after questions emerged during the Senate ethics committee investigation about his role in the Bachmann campaign.

The Associated Press contributed to this report.