The survey, which provided a brief overview of the administration’s arguments for the proposed changes and opponents’ arguments against it, showed 39 percent of adults opposed the administration’s proposal, with 33 percent supporting it. Twenty-nine percent did not register an opinion.

Support fell along party lines, with 59 percent of Republicans somewhat or strongly supporting the process to modify the vehicle standards, while 61 percent of Democrats somewhat or strongly oppose the effort.

“If you look 20, 30 years ago, you didn’t see this kind of split on environmental issues,” said Harvard University environmental law professor Jody Freeman by phone Tuesday. Freeman served as counselor for energy and climate change in the White House from 2009-10, where she worked on the agreement with automakers that led to the current regulations.

Forty-two percent of adults said they opposed the Trump administration’s additional proposal to remove California’s authority under current law to request a waiver to set emission standards for new motor vehicles that are stronger than federal ones. Sixteen percent of Democrats supported the move, compared to 48 percent of Republicans.