Murray Energy, once a symbol of American mining prowess, has become the eighth coal company in a year to file for bankruptcy protection. The move on Tuesday is the latest sign that market forces are throttling the Trump administration’s bid to save the industry.

The collapse of the Ohio-based company had long been expected as coal-fired power plants close across the country.

Its chief executive, Robert E. Murray, has been an outspoken supporter and adviser of President Trump. He had lobbied extensively for Washington to support coal-fired power plants.

Mr. Murray gave up his position as chief executive and was replaced on Tuesday by Robert Moore, the former chief financial officer. Mr. Murray, who will remain chairman, expressed optimism that the company would survive with a lighter debt load.