SIOUX FALLS, S.D. — South Dakota Gov. Kristi Noem said late Thursday it came as a surprise when a billionaire GOP donor reached out with a $1 million offer to fund the National Guard’s deployment to the U.S. border with Mexico.

The Republican governor spoke to reporters for the first time on Thursday after receiving intense scrutiny for accepting the donation. Critics have said it created a troubling precedent that effectively turned National Guard troops into soldiers-for-hire. But Noem described the transaction as a “wonderful” happenstance in which Willis Johnson, the billionaire Republican donor, gave her an unexpected phone call as she was deliberating where to come up with the money to send the National Guard or law enforcement officers to the border.

“It really was a surprise when he gave me that phone call and said that he wanted to help support the state of South Dakota,” Noem said.

The governor said she has not known Johnson long — their recent interaction was limited to a handshake and a short visit. But that’s all it took for Johnson to wire $1 million from his private foundation into state coffers.

Meanwhile, Democratic lawmakers, who hold just a handful of seats in the Legislature, have called on the governor to return the donation and cancel the deployment.

“Privatized deployments set dangerous precedent for further political use of our National Guard,” they stated in a letter sent to the governor’s office.