During his tenure, Mr. Pruitt pushed out numerous proposals to roll back environmental regulations. At least a half-dozen have been struck down by courts.
Three people close to Mr. Wheeler said he wanted to avoid rolling out a major policy that could be legally vulnerable. But Mr. Rosen, the deputy secretary of the Transportation Department, is confident that the proposal will stand up to legal challenge in part because of the changing makeup of the Supreme Court, according to a half-dozen people familiar with his thinking.
Mr. Rosen, a lawyer whose former clients have included General Motors and Hyundai, served as general counsel for the Transportation Department during the Bush administration, where he was known as an opponent of efforts to combat climate change and regulate auto pollution. People familiar with Mr. Rosen’s thinking say he now sees an opportunity to strip away regulations that he has fought for years.
“The thinking is, whatever they do to relax the standards, California will sue. So why not go for the whole thing?” said Myron Ebell, who led the Trump administration’s E.P.A. transition team.
With the retirement of the Supreme Court Justice Anthony M. Kennedy, who often served as a swing vote on the court, Mr. Trump has nominated a judge to succeed him, Brett Kavanaugh, who is considered more reliably conservative. “They may well feel emboldened by the fact that Kennedy is retired, and they will likely see more conservative justices,” said Jody Freeman, a professor of environmental law at Harvard and a former adviser to President Barack Obama.
However, Ms. Freeman noted that previous efforts to pre-empt such state-level authority have failed, a fact that also concerns Mr. Wheeler, according to people familiar with his thinking. “We’ve never seen a state-level waiver being revoked, and it’s not clear how that would work,” Ms. Freeman said.
Along with Mr. Rosen, Ms. King, the deputy administrator of the Transportation Department’s National Highway Traffic Safety Administration, backs an analysis showing that the Trump proposal would save lives in car accidents. Her analysis shows that the Obama rules would lead to as many as 12,000 more traffic fatalities.