President-elect Donald Trump is expected to nominate Scott Pruitt, the attorney general of the oil and gas-intensive state of Oklahoma, to head the Environmental Protection Agency, a move signaling an assault on President Obama’s climate change and environmental legacy. Pruitt has spent much of his energy as attorney general fighting the very agency he is being nominated to lead. He is the third of Trump’s appointees who have key differences with the agencies they have been tapped to run. Ben Carson, named to head the Department of Housing and Urban Development, has expressed a deep aversion to the social safety net programs and fair housing initiatives that have been central to that agency’s activities. Betsy DeVos, named education secretary, has a passion for private school vouchers that critics say undercut the public school systems at the core of the government’s mission.