“He may be able to do more through climate change [rules] because the EPA has the authority,” Sen. Richard Blumenthal (D-Conn.) told The Hill on Thursday.

The most far-reaching piece of Obama’s climate plan is carbon emission standards for the nation’s fleet of existing power plants, by far the largest single source of industrial carbon emissions. The EPA is also writing standards for new plants.

“I think climate change, immigration reform are both sort of legacy issues,” Blumenthal said. “The measure of his presidency will be whether he has left changes in law and regulation, but also a heightened awareness, which I think he has been doing.”

Princeton University professor Julian Zelizer said the push on climate change through executive action could shape Obama’s legacy — but only to a point.

“There are limits to what it will mean to his presidency,” said Zelizer, who teaches history and public affairs.