CHARLESTON, W.Va. — Former coal executive Don Blankenship went from prison to politics after serving a one-year sentence related to the deadliest U.S. mine disaster in four decades.

His quest: To take down the man he blames for fueling public distrust of him — Democratic U.S. Sen. Joe Manchin.

The self-funded Blankenship is among six candidates in the Republican Senate primary Tuesday, almost a year to the day since his release from a California prison. He has launched a scorched-earth advertising campaign aimed at Senate Majority Leader Mitch McConnell that some have labeled racist for its characterization of the Kentucky Republican's wife, Elaine Chao, who is the U.S. secretary of transportation.

Blankenship is "adding uncertainty to West Virginia politics," said Robert Rupp, a political history professor at West Virginia Wesleyan College. "And it's an obstacle for political observers to figure out what's happening. It threw all our calculations out."

Rupp said lower voter turnout for a midterm primary could enable Blankenship to wrestle victory away from U.S. Rep. Evan Jenkins and state Attorney General Patrick Morrisey. Despite Jenkins' credentials as a sitting congressman, his chances "may be troubled" by a crowded Republican field, Rupp said.

Blankenship, the former Massey Energy CEO, has poured $3.5 million of his own money into his campaign, far more than Jenkins and Morrisey. But what's lacking is outward backing from his own party.

"Let me be clear: I don't care who they are supporting," Blankenship said. "I am not for sale."

Jenkins and Morrisey have mostly focusing their campaigns on their own merits, and on criticism of Manchin and each other. Both have touted their own efforts to reduce the scourge of the opioid epidemic in the state, which leads the nation in the rate of drug overdose deaths, and have distanced themselves from McConnell.

Jenkins has made much of Morrisey's past lobbying ties to the pharmaceutical industry. Morrisey has gone after Jenkins' background when he was a Democrat before switching parties in 2013.

Rupp said the Senate race will be the most closely watched in West Virginia in a generation.

"At least we're going to get some attention," he said. "At issue is not just Republican continued control of the Senate. It's also a concerted effort to defeat a blue-dog Democrat in a red state."

West Virginia gave Donald Trump his largest margin of victory in the nation in 2016 in a state where Republicans make up just 32 percent of registered voters.

When Trump visited West Virginia in early April to tout his tax plan, Jenkins and Morrisey sat on either side of him. Blankenship wasn't there and didn't complain about it.

The 68-year-old Blankenship served a one-year prison term on a misdemeanor conviction for conspiring to violate federal mine safety standards at Massey's Upper Big Branch Mine, where 29 miners were killed in a 2010 explosion.

He's used his campaign to try to clear his name and blame the federal government for the explosion, in particular the policies of the Mine Safety and Health Administration under former President Barack Obama. Blankenship has used his website to repeatedly accuse Manchin of helping cover up the truth about the mine explosion.

Last year the U.S. Supreme Court rejected Blankenship's bid to have his appeal heard.

Four investigations found that worn and broken cutting equipment created a spark that ignited accumulations of coal dust and methane gas. Broken and clogged water sprayers allowed what should have been a minor flare-up to become an inferno. The federal jury held Blankenship at least partially responsible.

On Sunday, Morrisey said Blankenship had not filed a personal financial disclosure form for his candidacy in violation of the Ethics in Government Act. Blankenship campaign spokesman Greg Thomas responded that the candidate is "in the process" of filing the paperwork and that Blankenship's form is complicated.

Morrisey said he plans to forward information to Blankenship's probation officer to determine whether it's a violation of Blankenship's supervised release.

Manchin is seeking his second full six-year term and faces Paula Jean Swearengin in Tuesday's primary. He was West Virginia's governor during the mine explosion and said then that Blankenship "had blood on his hands." After Blankenship's release from prison, Manchin said he hoped Blankenship would "disappear from the public eye."

Instead, Blankenship filed his candidacy papers late last year, which has angered many in southern West Virginia who say it made them relive the 2010 tragedy.

A few miles north of the shuttered mine, retired teacher Shelia Anderson of Sylvester has been a lifelong Republican in Boone County, where Democrats outnumber them 3 to 1. Anderson said she prefers Manchin over Blankenship if they're paired in the fall.

"Don Blankenship hurt himself in this county," Anderson said. "Nobody hurt him."