American manufacturing has been in the doldrums for years, battered by high borrowing costs and a strong dollar, which makes exports less competitive. But there has been a bright spot: billions of dollars flowing into factory construction, signifying that a potential rebound in production and employment is around the corner.

The flood of investment has been driven by two major categories of subsidies provided under the Biden administration. One offered incentives for the construction of several enormous semiconductor plants set to begin operation in the coming years. The other supercharged the production of equipment needed for renewable energy deployment.

This second category is in jeopardy as the Trump administration and the Republican-led Congress seek to roll back support for low-carbon energy, including battery-powered vehicles, wind power and solar fields.

One option to raise money to offset the cost of their desired tax cuts is truncating credits for renewable power generation.

“If it ends up that the timeline for these credits is shortened, then the incentives to develop an onshore manufacturing facility obviously go down,” said Jeffrey Davis, a lawyer with White & Case who specializes in renewable energy incentives. “If you’re looking at the prospect of sales and revenue over a three-year period instead of an eight-year period, the manufacturing facility may not pencil out.”

The Biden administration’s strategy relied on a push and a pull. First, push the supply of clean energy products through tax breaks, loans and direct grants to manufacturers. Equally important was pulling demand along: rebates for buying electric cars, tax credits for producing renewable power, and subsidies for states and individuals to install solar arrays. Companies contemplating manufacturing investments took both sides into account when planning where to build or expand a plant.

And there were big bets on the electrified, sun- and wind-powered future — $89 billion in private investment went into clean energy manufacturing in the two years that ended in September, according to the Rhodium Group, an economic research firm. Auto companies have retooled production lines for electric vehicles and entered into joint ventures to make batteries, while mines and processing facilities are under development to supply the minerals that go into them.

Some of those facilities are operating, and some are under construction. But plenty are still just planned. And those companies are mulling whether to move forward, especially with the winds against them in Washington.

“Are we going to compete or not? That’s the question automakers are going to be asking themselves,” said Harrison Godfrey, head of federal investment and manufacturing at Advanced Energy United, an industry association. “Is there enough of a demand-side market here to help me continue this investment?”

For several parts of the renewable energy supply chain, the economics were already challenging. Some projects were halted before the November election. For others, President Trump’s victory was the final straw.

“President Trump campaigned on dismantling the Green New Scam, and that’s precisely what he’s doing,” a White House spokesman, Harrison Fields, said.

Take hydrogen, which is envisioned as an energy source both for truck freight and for industrial facilities. Nel, a Norwegian company that makes electrolyzers needed for hydrogen production, thought the Inflation Reduction Act would drive enough demand in North America to add a manufacturing facility in Michigan.

Together with federal tax breaks and additional funding from the state, Nel gathered nearly $200 million in state and federal money to build the plant, which would have employed about 500 workers. But the regulations governing the tax credit for hydrogen producers didn’t come out until last month, delaying any solid orders.