After more than a decade of false starts, lawmakers in Washington are on the cusp of advancing a bill to reform the Byzantine system for approving projects needed to modernize power grids, build artificial intelligence data centers and revitalize clean energy development.

The Democrats’ sweeping victories in the midterm elections, however, has tossed a wrench into the effort.

Senators are now fighting to preserve a bipartisan permitting reform deal reached after months of painstaking negotiations, with a procedural vote on the bill set for Monday. Congress has two short months to pass the plan, which overhauls how projects including pipelines, power lines and solar and wind farms are approved.

House Minority Leader Hakeem Jeffries is opposing the bill in its current form, arguing it hasn’t received enough input from House Democrats. Other progressive Democrats say they should use their newfound control of Congress next year to negotiate for a better deal. The legislation is also facing mounting opposition from Native American tribes and environmental groups.

“The path to this has gotten more difficult,” said Chris Moyer, a Democratic strategist who has worked for former Senate Majority Leader Harry Reid and other lawmakers. “Every two years the party that takes power says let’s hold off for a better deal.”Addressing the permitting system is a top priority for President Donald Trump’s administration. The energy industry has long complained about the regulatory hurdles in the US, which can add years of red tape delays and millions of dollars to renewable power and oil and gas projects alike. Reform has been floated for more than a decade, but there’s been little progress.

The latest effort aims to address government reviews that are slow and overlapping, but opponents say it does away with crucial environmental safeguards. The bill would impose deadlines on government reviews under the National Environmental Policy Act and changes other laws considered sacrosanct by environmentalists.

Senator Sheldon Whitehouse, a Rhode Island Democrat, led negotiations on the deal. He is the top Democrat on the Senate environment committee and his constituency is home to a major offshore wind project. He said input on the bill has already been solicited from House members and the bill’s authors on Saturday released an amendment designed to address concerns they raised. “A good permitting bill comes together over years of complex negotiations,” Whitehouse said in a statement. “We don’t have more years to lose as clean energy projects sit on the sidelines.”Jeffries said through a spokesman he is opposed to the plan as drafted and would “not rubber-stamp legislation that emerges from the Senate” without more involvement from the Democratic House caucus, according to Politico.

TD Cowen, in a note to clients the morning after election day, said they were reducing the likelihood of lame duck passage of the bill from 40% to 25%, on grounds it likely emboldens voices arguing that the bill gives too many concessions to the oil and gas industry.

Democratic Senators Whitehouse and Martin Heinrich of New Mexico, as well as Republican Senators Shelley Moore Capito of West Virginia and Mike Lee of Utah unveiled the 417-page draft before Congress took a monthlong break for the midterm elections.

Backers of the measure range from the American Petroleum Institute and the American Clean Power Association, which has lauded language in the bill that would make it easier to build high-voltage power lines.

But opponents fear it could undermine sovereignty of Native American tribes and cause lasting environmental damage.

“As currently drafted, this bill will hand more power to the executive branch, erode democratic norms, and cause environmental harm to our water, wildlife, and public health protections far beyond the scope of federal permitting,” Loren Blackford, executive director of the Sierra Club, said in a statement on Friday.