This past weekend, conservative Democratic Senator Joe Manchin of West Virginia announced that, after months of negotiations with the White House, he wouldn't be supporting Build Back Better—President Joe Biden's ambitious $2 trillion economic package aimed at protecting workers, expanding education access, and fighting the climate crisis.

Because Senate Democrats need all 50 of their members to support the bill and bypass a Republican filibuster, Manchin's announcement dealt the toughest blow yet to the legislation's passage, though the White House still expressed hope that Manchin would be open to further negotiations.

Now, America's largest mine workers union—the United Mine Workers of America (UMWA)—has joined the chorus of voices urging Manchin to reconsider.

It's an important development because Manchin's home state of West Virginia is coal mining country. A 2019 study found that coal mining industries accounted for 17 percent of the state's total economic output. West Virginia accounts for more than a quarter of all the coal industry jobs in America. The state remains the second-largest coal producer in the nation, behind Wyoming.

Throughout his 2018 reelection campaign, Manchin emphasized the importance of "keeping promises to our miners," but the statement from UMWA's president, Cecil Roberts, highlighted all the ways the Senator's opposition to Build Back Better would hurt them.

The statement read in part:

“The bill includes language that would extend the current fee paid by coal companies to fund benefits received by victims of coal workers’ pneumoconiosis, or Black Lung. But now that fee will be cut in half, further shifting the burden of paying these benefits away from the coal companies and on to taxpayers.”

It continues:

“For those and other reasons, we are disappointed that the bill will not pass. We urge Senator Manchin to revisit his opposition to this legislation and work with his colleagues to pass something that will help keep coal miners working, and have a meaningful impact on our members, their families, and their communities.

Roberts also went on to voice support for voting rights legislation, which is currently stalled in no small part due to Manchin's opposition to filibuster reform.

People celebrated the statement on Twitter.

Others, citing Manchin's immense wealth, were more skeptical.

Manchin has yet to respond to the union's concerns.