West Virginia Gov. Jim Justice switched parties to join Republicans as President Donald Trump visited the increasingly conservative state.
Justice's plans were confirmed to The Associated Press on Thursday by a Democratic Party official with knowledge of his plans. The official spoke on condition of anonymity because he was not authorized to discuss the decision before the announcement.
The governor announced his decision Thursday evening at a campaign rally with the president.
WATCH: West Virginia governor switches to Republican Party
Justice was elected in November with just 49 percent of the vote, 20 percentage points behind Trump's total in the presidential contest in the state. Trump won 77 percent of West Virginia's Republican primary voters in May.
The president promised throughout the campaign to resurrect the lagging coal industry that has declined amid changing energy markets, leaving many West Virginia communities devastated. The industry and many of its workers have blamed the decline mostly on former President Barack Obama and his environmental policies.
Justice's defection leaves Democrats with just 15 governors among 50 states.
In West Virginia, his jump is another blow for Democrats in a state they once ran without opposition. U.S. Sen. Joe Manchin and state Treasurer John Perdue will be the remaining statewide elected Democrats.
Manchin is up for re-election in 2018, one of 10 Democratic senators running in states Trump won, a dynamic that gives Democrats an uphill path to reclaiming a Senate majority.