A bipartisan deal to speed energy development is facing concerns it could favor natural gas over renewables because of President Trump's opposition to wind and solar.

Why it matters: The worries from Rep. Sean Casten (D-Ill.) could complicate efforts to pass the bill before year's end, highlighting divisions even among Democrats who have long supported permitting reform.

Driving the news: Casten, a former energy executive and leading Democratic voice on permitting reform, said he isn't yet backing the bill and is negotiating changes with Senate Democrats to prevent it from disproportionately benefiting natural gas.

"My test for the bill is: I talk to energy developers, and ask, 'What would you build in response to this bill?' And the answer I get overwhelmingly is a lot of gas," Casten told Axios on stage at a University of Chicago event Wednesday.

"I think you have to look at the bill in the context of everything else that the Trump administration has done."

The big picture: The AI boom is fueling demand for electricity, prompting a rush to build natural gas power plants alongside renewable energy projects. The permitting deal could help determine which technologies benefit most from that expansion.

Catch up quick: The bill, sponsored by two Republicans and two Democrats who lead the Senate's energy and environment committees, would speed construction of power lines and other energy infrastructure.

An initial procedural vote is scheduled for Nov. 9, shortly after the midterm elections, setting up a potential push to pass the legislation before the new Congress takes office.

Threat level: The bill aims to prevent political favoritism in energy permitting, but Casten worries one provision could have the opposite effect.

It would allow developers to challenge discriminatory permitting decisions in part by comparing them with decisions made over the previous five years.Casten argues that as Trump's second term becomes part of that historical benchmark, the administration's treatment of renewable energy could effectively become the new normal.

What we're hearing: The five-year provision is emerging as a concern in negotiations over the bill.

"This is definitely one of the key issues that folks are thinking about right now," said an industry official tracking the negotiations closely, who spoke on the condition of anonymity to discuss congressional feedback.Clarifying or strengthening the language would "go a long way to reassuring folks who are on the fence," the official added.

Zoom out: Divisions among Democrats are emerging about the overall bill. Former Energy Secretary Jennifer Granholm and climate activist Tom Steyer are urging its passage, while four Senate Democrats are demanding the restoration of canceled clean-energy grants and Rep. Rashida Tlaib (D-Mich.) is calling for its defeat.

Yes, but: Casten also praised the bill's overall structure and said relatively small changes could win his support. He's negotiating those changes with Sens. Sheldon Whitehouse (D-R.I.) and Martin Heinrich (D-N.M.).

"I think the structure of the bill is good," he said. "I think there are modest changes we could make to it to make sure it works and doesn't sort of create like a gold rush for gas."He favors passing the bill before year's end, unlike some Democrats who have suggested waiting to see whether the midterm elections give their party more power next year.

What they're saying: The White House said it supports the bipartisan deal and is pushing for a vote.

"The text of the legislation has been published, and all that is left to do is vote. We are in direct conversations with the lead negotiators in the Senate," a White House official said.A Heinrich spokesperson said the bill "will expedite the approval of clean energy projects and put more clean, cheaper electricity on the grid."

The bottom line: The midterms could upend these delicate negotiations just days before the Senate's Nov. 9 procedural vote.

Editor's note: Amy is a journalism fellow at the University of Chicago's Institute for Climate and Sustainable Growth and moderated Wednesday's event featuring Casten.