WASHINGTON—Don Blankenship, the former coal magnate who served a year in prison for a mine-safety conviction, said Monday that he planned to continue his bid for a U.S. Senate seat, now as a third-party candidate after losing the Republican primary in West Virginia earlier this month.

Mr. Blankenship’s decision to remain in the race—as a candidate for the Constitution Party—follows his vow days after the May 8 primary that “it’s not over.” In addition to giving him a second shot at facing Democratic Sen. Joe Manchin in November, it enables him to extend his feud with Senate Majority Leader Mitch McConnell, who opposed his candidacy in the GOP primary.

Mr. Blankenship’s third-party hopes are complicated by West Virginia’s “sore loser” law, which was designed to prevent failed candidates of a recognized political party from refiling to run under another party’s banner.

“Now that we know that the establishment will lie and resort to anything else necessary to defeat me, we are better prepared than before,” Mr. Blankenship said Monday, adding he planned to challenge the “sore loser” law in court.

President Donald Trump also spoke out against Mr. Blankenship’s bid for the GOP nomination.


West Virginia Attorney General Patrick Morrisey won the Republican Senate primary and will face Sen. Manchin in November. Mr. Manchin is counted among the Senate Democrats’ most vulnerable incumbents, given Mr. Trump’s wide margin of victory in the state in 2016.

A super PAC aligned with Mr. McConnell provided $1.4 million to another super PAC that spent all of its money on TV ads attacking Mr. Blankenship as too toxic for the Senate, according to a Federal Election Commission report filed Sunday.

The group, Mountain Families PAC, raised no money from any other source and had not disclosed its funding ahead of the primary, the filings show.

The Senate Leadership Fund is stocked with ex-McConnell aides. It spent $1.8 million in April, the new report shows, the majority of it in West Virginia.


For his part, Mr. Blankenship attacked Mr. McConnell in his own advertising, calling him “Cocaine Mitch,” a reference to an allegation that drugs were found during an inspection in Colombian waters on a ship owned by his father-in-law’s company. Neither Mr. McConnell’s office nor the company have commented on the allegation. Mr. Blankenship spent at least $4 million on his primary race, FEC reports show.

Mr. Blankenship changed his party registration to the Constitution Party on Monday and has until Aug. 1 to submit a signature petition plus a certificate of nomination by the party, said Steven Adams, a spokesman for the secretary of state.

A representative of the West Virginia Constitution Party, which says on its website it affirms “the Christian character and heritage of our State” and the Bible as the foundation of the law, didn’t immediately respond to a request for comment.

“We feel that the [sore loser] law is pretty plain in that it was designed to prevent this sort of repeat candidacy,” Mr. Adams said.


However, Robert Bastress, a West Virginia University law professor who has litigated election-law cases in the state, predicted a court battle. He pointed to a tense issue in the letter of the law, which refers to “candidates who are not already candidates in the primary election for public office.”

Having lost the primary, Mr. Blankenship is technically no longer a candidate. “At a minimum, the statute is ambiguous,” Mr. Bastress said.

—Siobhan Hughes contributed to this article.

Write to Julie Bykowicz at julie.bykowicz@wsj.com


Corrections & Amplifications

West Virginia’s primary was on May 8. An earlier version of this article incorrectly stated it was on May 10. (May 21, 2018)