Republican candidate for U.S. Senate Don Blankenship speaks at a town hall meeting at West Virginia University on March 1  in Morgantown. (Spencer Platt/Getty Images)

A controversial Republican candidate for U.S. Senate in West Virginia accused Senate Majority Leader Mitch McConnell (R-Ky.) this week of having a potential conflict of interest related to his father-in-law, whom he called a “wealthy Chinaperson.”

Don Blankenship, a former coal executive who has served a year in prison for conspiring to violate mine safety and health standards after a 2010 underground explosion killed 29 miners, brought up McConnell’s wife, Elaine Chao, in a local radio interview Monday. Chao, the secretary of transportation in the Trump administration, immigrated to the United States from Taiwan as a child. Her father, who was born in China, founded an international shipping company.

“I have an issue when the father-in-law is, you know, is a wealthy Chinaperson and there’s a lot of connections to some of the brass, if you will, in China,” Blankenship said in an interview on 106.3 The River.

“I read in books that people think he’s soft on China,” Blankenship said of McConnell. He did not provide any evidence backing up such claims.

Blankenship said: “A lot of these senators, including Mitch, you know, have the potential for a conflict of interest. They need to be a lot more transparent about it than they are.”

In a Wednesday interview with Fox News Channel, McConnell dismissed Blankenship’s remarks.

“Well, my father-in-law is an American who lives in New York, works in New York and I don’t have any comment about ridiculous observations like that,” he said.

Josh Holmes, McConnell’s former chief of staff and one of his top political advisers, wrote on Twitter: “This candidate is as contemptible a human being as you will find.”

Blankenship has ties of his own to China. His fiancee was born there, the New York Times reported. A Blankenship spokesman did not immediately confirm that information but said he would seek more clarity on the matter.

Blankenship has also previously said he was “considering moving to China,” according to audio of a prior conversation obtained and published online by the Charleston Gazette-Mail.

Senate GOP leaders have voiced concerns that Blankenship’s past will hurt Republican chances of defeating Democratic Sen. Joe Manchin III in the general election. An organization called Mountain Families PAC that has ties to McConnell allies has run advertisements criticizing Blankenship.

Blankenship’s two main GOP opponents are Rep. Evan Jenkins and state Attorney General Patrick Morrisey. The primary is May 8.

Republicans are defending a 51-to-49 Senate majority in the midterm elections. They view West Virginia as one of their best pickup opportunities.

Even as Blankenship called for more transparency when it comes to McConnell, his own secrecy has drawn scrutiny. The Senate Office of Public Records confirmed Wednesday that Blankenship had not submitted his required personal financial disclosure.