Among other changes, one amendment removed language that would have guaranteed union-level wages for workers on projects funded through the legislation, and another delayed the effective date to June 1 to lower the vote total needed to pass the bill. Bills passed in the veto session that take effect immediately need three-fifths majorities in both chambers.

Sen. Chapin Rose, R-Mahomet, who also represents the Clinton plant and sponsored the legislation in the Senate, said passage appeared uncertain for much of the day. Rose credited Rauner for getting involved in negotiations over the last two weeks, which he said ended up producing a stronger bill.

After the administration weighed in, Exelon dropped a controversial proposal to change the way customers are charged for their power.

The so-called “demand charge,” based on a monthly average of peak demand rather than overall consumption, drew widespread criticism from consumer groups and the Illinois attorney general’s office. Critics said it could have created unpredictable bill spikes.

“The biggest brick on this bill was that demand charge because … there was no defense to it, frankly,” Rose said, adding that it wouldn’t have come out without Rauner’s involvement.