For two years, the Trump administration and Republicans in Congress have exerted almost absolute control of US environmental policy, reorienting government support away from climate action, clean energy and stricter pollution controls to further embrace fossil fuels and deregulation.

That’s about to change in a big way. After securing decisive majorities in both the House and Senate in a historic blue wave Tuesday, Democrats will have new leverage. Former officials and policy experts expect them to use it to step up scrutiny of the Trump administration’s record on energy and the environment. The shakeup could also complicate, or sink, a bipartisan deal on permitting reform.

With both chambers flipped, Democrats next session will set the agenda for hearings and will wield investigative powers, able to issue subpoenas for officials and industry to testify or produce documents for review. Their victory allows for a level of oversight that’s simply not possible for the minority party.

Appropriations could be a focus, given that the Trump White House has repeatedly frozen and withheld funds appropriated by Congress, such as for National Science Foundation and Environmental Protection Agency grants.

“I would expect Congress to reassert its oversight of the budget and start looking at what they’re going to do to enforce that,” said Josh Freed, senior vice president for the climate and energy program at the liberal think tank Third Way.

Democrats are planning investigations into Interior Secretary Doug Burgum and his team, including over the bungled Lincoln Memorial Reflecting Pool upgrades and officials’ dealings with oil and gas companies, Politico has reported. EPA chief Lee Zeldin may also face scrutiny, especially since Representative Zoe Lofgren, a California Democrat and ranking member of the House Committee on Science, Space, and Technology, recently accused him of failing “to produce a single responsive document, communication, or record” after myriad requests.

Another possible target of investigators: businesses that made deals with or got regulatory reprieves from the administration.

“Democrats with gavels and subpoena authority in one or both chambers are going to put significant countervailing pressure on industry,” said Zealan Hoover, who was a senior EPA advisor during the Biden administration. He anticipates congressional reviews of companies that cut deals to trade offshore wind leases for fossil fuel infrastructure and got out of Clean Air Act requirements.

As election returns rolled in on Tuesday night, Senator Ed Markey of Massachusetts, a Democrat on the Committee on Environment and Public Works, posted on X, “They are going to need to plant new forests for all of the subpoenas we’ll be printing.”Clinching the Senate as well as the House means Democrats will have more resources to dedicate to investigations. They’ll also have more power to block Trump nominees for senior agency and judicial jobs going forward.

The midterms also have the potential to impact policy before the next session of Congress — through the fate of the controversial permitting reform bill, the Bipartisan American Affordability and Jobs Act, or BAAJA. A handful of Republicans and Democrats in the Senate announced in late September that they’d secured a deal to speed up the approvals of pipelines, power lines and other infrastructure projects. But since then, a number of Democrats, environmentalists and other stakeholders have raised concerns with the proposal.

Going into the elections, senators were planning to introduce an amendment to the bill in the coming days, followed by a procedural vote and final vote within weeks; the House likely wouldn’t vote until after Thanksgiving.

But it’s an open question whether there’s sufficient Democratic support to pass the deal now. There’s a possibility that the party decides to punt discussions down the road to when they also control the White House, some policy experts have warned, noting that Trump has already threatened to veto any legislation coming out of a Democrat-controlled Congress. If they drop the issue now, there’s a strong chance that an alternative doesn’t pass until there’s a Democratic president.