WASHINGTON — When President Trump chose the Oklahoma attorney general, Scott Pruitt, to lead the Environmental Protection Agency, his mission was clear: Carry out Mr. Trump’s campaign vows to radically reduce the size and scope of the agency and take apart President Barack Obama’s ambitious climate change policies.

In his first weeks on the job, Mr. Pruitt drew glowing praise from foes of Mr. Obama’s agenda against global warming, as he moved to roll back its centerpiece, known as the Clean Power Plan, and expressed agreement with those who said the E.P.A. should be eliminated. His actions and statements have galvanized protests from environmentalists and others on the left.

But now a growing chorus of critics on the other end of the political spectrum say Mr. Pruitt has not gone far enough. In particular, they are angry that he has refused to challenge a landmark agency determination known as the endangerment finding, which provides the legal basis for Mr. Obama’s Clean Power Plan and other global warming policies.