WASHINGTON — As a group of progressive activists and constituents prepared for a 15-minute meeting on Wednesday with Senator Susan Collins, Republican of Maine, they sat in the lobby of her office and developed a last-ditch strategy to persuade her to vote against the $1.5 trillion tax bill barreling through Congress: tears.

“If Senator Collins actually saw you as a human, saw me as a human, then she wouldn’t pass any of this,” said Ady Barkan, a member of the Center for Popular Democracy, who recently learned he had amyotrophic lateral sclerosis, or A.L.S., and uses a wheelchair.

Ms. Collins, after weeks of wavering, cut several deals with Republican leaders in exchange for going along with the tax overhaul that passed the Senate this month and is on track to be sent to President Trump by Christmas. Among other things, the Senate version of the bill would repeal the Affordable Care Act requirement that most Americans have health insurance or pay a penalty.

Among the provisions she secured was support for bipartisan health care legislation to stabilize the Affordable Care Act’s insurance markets, whose prices could increase if the mandate repeal is enacted. She also claims to have a commitment from Republican leaders to prevent automatic Medicare spending cuts that could occur as a result of arcane budget rules that would kick in after the tax cut is passed.