Illinois Democratic Gov. JB Pritzker remained optimistic Tuesday that a deal could still be struck on clean-energy legislation after an 11th hour negotiating glitch torpedoed the last remaining unresolved big-ticket item on lawmakers’ spring session agenda.

Pritzker’s office had brokered what it thought was a tentative agreement with one of the largest players in the energy legislation push, Exelon Corp, to raise ratepayer subsidies by more than $600 million over five years to stave off the possible closure of three of its Illinois nuclear power plants.

But the deal collapsed during the wee hours Tuesday when Senate Democrats and Senate President Don Harmon, D-Oak Park, balked at unrelated provisions in the package to phase out coal-powered energy plants by 2035.

In particular, there were concerns about that impact on a multibillion-dollar coal plant in far southern Illinois, the Prairie State Energy Campus, which was partially bankrolled by a handful of Chicago suburbs like Naperville, Winnetka, St. Charles, Geneva and Batavia that receive their power from that plant.

Pritzker, who had been championing an array of other clean-energy components as part of the energy bill, said Tuesday he wants lawmakers to finish the job and get legislation to his desk.

“We have done everything we can to stand up for clean energy principles to make sure we’re expanding renewables in this state,” Pritzker told reporters in his statehouse office. “I’ve set out my principles. I’ve stuck by those principles. My hope is we wind up with a good energy bill. We were very close as of last night. I’m really hopeful.”

The package now in limbo also contained incentives for wind and solar power generators, aimed to make Illinois’ power generation industry carbon-free by 2050 and phased out a highly lucrative ratemaking formula in use by Exelon’s scandal-tainted subsidiary, Commonwealth Edison.

With the pressure seemingly now eased, it’s not clear when the Democratic-led legislature will take up the matter again. The House and Senate are not scheduled to be in Springfield until the fall legislative session, though Pritzker or the legislative leaders could convene the General Assembly into a special session before then.

Harmon did not respond to an interview request Tuesday from WBEZ to explain his concerns or offer an outlook for the measure, but his office issued a statement pledging cooperation with Pritzker.

“I’m informed that an agreement has been reached between the governor and Exelon on a proposal that would save jobs, which has been our goal all along. That’s why we support the governor in these talks,” Harmon said. “We also stand with the governor on de-carbonization targets that need to be in a final deal.”

In a statement, a spokeswoman for Prairie State said it’s willing to look for ways to reduce carbon emissions, but continued its argument for being exempt from being phased out in 2035.

“Prematurely shuttering Prairie State in 2035 would place new financial burdens on communities who own the plant by essentially forcing them to pay for two sources of power: the energy already owned through their partnerships with Prairie State Energy Campus, and replacement power to cover that loss,” said Alyssa Harre, Director of External Affairs and Organizational Strategy for Prairie State. “That is an additional cost our not-for-profit member communities and their ratepayers cannot afford.”

The Senate had not adjourned as of late Tuesday afternoon and Harmon even hinted an energy vote could be imminent — even Tuesday. But there were no apparent signs of legislative movement toward that end.

“We stand ready to return to the Capitol when the governor’s plan is ready for action,” Harmon said.

As hopes faded, questions abounded over the relationship Harmon’s chief of staff, Jacob Butcher, has with the energy issue. Before becoming the Senate president’s top aide, Butcher was a Springfield lobbyist, whose law firm represented the southern Illinois coal plant that emerged as a sticking point.

Pritzker did not directly address whether he thought Butcher had a conflict of interest in his current role when asked about the aide’s past ties to Prairie State.

“I expect that all the people I work with in government will be focused on doing the right thing for the people of Illinois. I expect everybody that works in the General Assembly, everybody that works for the General Assembly will do that,” the governor said.

“I think integrity in government is extraordinarily important,” he said.

A Harmon spokesman did not respond to a WBEZ question about Butcher and Prairie State.

Dave McKinney and Tony Arnold cover Illinois politics and government for WBEZ. Follow them on Twitter @davemckinney and @tonyjarnold.