Republican candidate for U.S. Senate Don Blankenship speaks at a town hall meeting at West Virginia University on March 1, 2018 in Morgantown, West Virginia.

Voters in the heart of Trump country are ready to decide the fate of Don Blankenship, a brash West Virginia businessman and GOP outsider with a checkered past who is testing the appeal of President Donald Trump's outsider playbook in one of the nation's premiere U.S. Senate contests.

The stakes are high for a Republican Party bracing for major losses in this fall's midterm elections. A victory on Tuesday for Blankenship, an ex-convict who has run racially charged ads, could cost Republicans a Senate seat come November. But the anti-establishment fervor unleashed by Trump's 2016 campaign has proved difficult for GOP leaders to rein in.

On the eve of West Virginia's Senate primary election, Trump himself warned on Twitter that a Blankenship win would destroy Republicans' chance of defeating Democratic Sen. Joe Manchin in November.

Blankenship "can't win the General Election in your State...No way!" the president wrote of the retired coal executive, who was released from prison last year for his role in the deadliest U.S. mine disaster in four decades.

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Firing back at the Republican president, Blankenship described himself as "Trumpier than Trump" as he shrugged off Trump's call for local Republicans to support one of his two opponents.

"West Virginia will send the swamp a message: No one, and I mean no one, will tell us how to vote," Blankenship declared.

On Tuesday, West Virginia will join Indiana, North Carolina, and Ohio in hosting primary elections in states Trump carried in 2016. The Republican contests largely feature candidates jockeying to be seen as the most conservative, the most anti-Washington and the most loyal to the president.

In Indiana, Republicans will pick from among three Senate candidates who have spent much of the race praising Trump and bashing one another. The winner will take on another vulnerable Democrat, Sen. Joe Donnelly, this fall.

In Ohio, Republicans will likely nominate a more conservative candidate than outgoing GOP Gov. John Kasich, a 2016 presidential candidate and frequent Trump critic. Even Kasich's former running mate, Lt. Gov. Mary Taylor, has pledged to unwind some of Kasich's centrist policies, including the expansion of the Medicaid government insurance program.

Ohio also features primary elections in both parties to decide the candidates for an August special election to replace GOP Rep. Pat Tiberi, who resigned earlier in the year.

North Carolina Republicans will weigh in on the fate of Republican Rep. Robert Pittenger, who faces a primary challenger who almost upset him two years ago. Pittenger features Trump prominently in his campaign, while challenger Mark Harris, a prominent Charlotte pastor, has called Pittenger a creature of Washington who refuses to help Trump "drain that swamp."

Yet none of Tuesday's contests is expected to have more impact on the 2018 midterm landscape than West Virginia.

Blankenship has embraced Trump's tactics — casting himself as a victim of government persecution and seizing on xenophobia, if not racism — to stand out in a crowded Republican field that includes state Attorney General Patrick Morrisey and Republican congressman Evan Jenkins.

Republicans have long seen the state as a prime opportunity to expand the party's two-seat majority in the Senate by defeating Manchin. On paper at least, the GOP prospects look good: No state gave Trump a larger margin of victory than West Virginia, where Trump defeated Democrat Hillary Clinton by 42 points.

Yet Republicans across Washington are convinced that Blankenship, an unapologetic conservative who lives part-time near Las Vegas, cannot defeat Manchin.

In addition to Trump's warning, the head of the Senate Republican campaign arm has highlighted Blankenship's criminal history. And a group allied with the national GOP, known as Mountain Families PAC, has spent more than $1.2 million in attack ads against Blankenship in recent weeks.

The retired businessman was released from prison less than a year ago for his role in a 2010 mine explosion that left 29 men dead. Blankenship led the company that owned the mine and was sentenced to a year in prison for conspiring to break safety laws, a misdemeanor.

He has repeatedly blamed government regulators for the disaster, casting himself as the victim of an overzealous Obama-era Justice Department — an argument Trump regularly uses to dismiss federal agents investigating his campaign's ties to Russia.

Blankenship has used race and ethnicity to appeal to supporters in the campaign's final days, just as Trump did throughout his campaign.

The Senate candidate took aim at Senate Majority Leader Mitch McConnell, R-Ky., in an ad claiming that McConnell has created jobs for "China people" and that his "China family" has given him millions of dollars. McConnell's wife is U.S. Transportation Secretary Elaine Chao, who was born in Taiwan.

Blankenship also called McConnell "Cocaine Mitch" in a previous ad. That reference stems from a 2014 magazine article alleging drugs were found aboard a commercial cargo ship owned by Chao's family.

Arizona Republican Sen. Jeff Flake, a frequent Trump critic, suggested that Blankenship presents a moral problem for the GOP, not just a political one. He said he's ready to donate to Manchin's campaign if Blankenship becomes the GOP nominee.

"You get somebody like that in the Senate, you might get us one seat but you lose your soul," Flake said.