On Thursday, the state legislature signed off on $28 million in emergency state spending for Flint requested by Gov. Rick Snyder, who has also asked the federal government to expand Medicaid to cover every Flint resident younger than 21.

Democrats said they would attach their measure — which may rankle Republicans, especially those who have resisted federal emergency disaster aid for other states in the past — to a sweeping energy bill now on the Senate floor. They also suggested that they could filibuster that bill if their Flint package was not approved. “We’ve not yet made that decision,” said Senator Debbie Stabenow, Democrat of Michigan. “But this is very serious.”

The amendment is one among several expected to be attached to the bill by both Republicans and Democrats, part of the open amendment process favored by Senator Mitch McConnell, Republican of Kentucky and majority leader, but one which threatens the ability to pass bipartisan legislation like the energy legislation.

Republicans, for instance, are considering an amendment to undo a recent Interior Department moratorium on new coal mining leases on public lands, a measure that would undermine the bill’s chances of being signed by President Obama.

Democrats said the federal government had a responsibility to help Flint, where the drinking water was found to have elevated levels of lead after the city switched its water supply from Lake Huron to the Flint River. A study found the percentage of Flint children with high lead levels more than doubled after the switch.