In her 12 years in the State Capitol, Senator Patricia Fahy has consistently supported the carmaker Tesla’s complicated fight to open dealerships in New York, framing her position as a way of advancing the state’s green energy transition.

Things have changed.

After President Trump’s victory last fall, and the polarizing work by the billionaire Elon Musk, Tesla’s chief executive, to lead the Department of Government Efficiency, Ms. Fahy is no longer on Tesla’s side.

Ms. Fahy, a Democrat whose district includes Albany, and other state lawmakers are pushing to revoke a legislative waiver that has let Tesla directly operate five New York dealerships rather than sell cars through dealer franchises, as other carmakers must do.

Her fight with the company has extended beyond the State Capitol, with Ms. Fahy participating in demonstrations against a planned Tesla dealership just outside her district, in Colonie, N.Y.

“Maybe I’m making amends,” Ms. Fahy replied when asked about her previous support for Tesla. Mr. Musk, she said, is “part of an administration that is killing all the grant funding for electric vehicle infrastructure, killing wind energy, killing anything that might address climate change. Why should we give them a monopoly?”

Her turnabout reflects the growing sense of outrage that has touched off a nationwide protest movement against Mr. Trump and Mr. Musk, resulting in the defacing of Teslas and arrests during protests at the company’s factories and showrooms.