WASHINGTON — Democrats unilaterally drove major reforms to the health insurance and the pharmaceutical industries without a single Republican vote in recent years. But hospitals may be a health care giant they’re unable to confront alone.

Unlike Republicans, Democrats have seized on lowering health care costs as a politically winning issue in one election cycle after another. They have campaigned on passing health insurance reform, and then protecting it. And after 20 years, they finally delivered on a promise to empower the federal government to lower drug prices in 2022.

But the remaining elephant in the room is hospital costs, which make up the biggest share of U.S. health care spending. And Democratic leaders in Congress have shown this year that they are unable to agree on even the most incremental steps toward addressing the cost of hospital care.