From inmate to candidate: Who is Don Blankenship?

60 Minutes reported on the conviction of coal king Don Blankenship after a deadly mining explosion. After a year in prison, Blankenship ran for Senate

Voters on Tuesday head to the polls for primary elections in Ohio, Indiana, West Virginia, and North Carolina. The country will be focused on West Virginia's Senate primary, where dark-horse candidate Don Blankenship — a former coal CEO — is vying for the chance to challenge Democratic Sen. Joe Manchin in November.

West Virginia's primary has become a national news story because Blankenship was in prison as recently as a year ago. The former CEO of Massey Energy, he was convicted of conspiring to violate federal mine safety and health standards in the months ahead of a deadly mine explosion that killed 29 miners in 2010. He was sentenced to 12 months in prison and released last May.

It was the first time in U.S. history that a CEO of a major company was convicted of a workplace safety crime; 60 Minutes correspondent Anderson Cooper reported on his conviction in the 2016 story "King of Coal."

"This was a coal mine and a company that was — it's not an exaggeration to say — run as a criminal enterprise," Assistant U.S. Attorney Steve Ruby told Cooper. Ruby led the prosecution against Blankenship, along with U.S. attorney for West Virginia Booth Goodwin.

"This could be likened to a drug organization, and the defendant was the kingpin," Goodwin told Cooper.

Blankenship declined to speak with 60 Minutes.

As Cooper reported, prosecutors said he condoned and tolerated safety violations for the sake of profit. They said was aware of his company's safety problems because he was a micromanager who had oversight over every aspect of Massey mines, personally approving every hire, hourly raise, and capital expenditure.

President Trump on Monday pleaded with voters to oppose Blankenship because he fears the former mine operator will lose a general election.