President Trump is expected as soon as next week to order the Environmental Protection Agency to rescind its Clean Power rule that is blocked by the courts. But the President faces another test of political fortitude on whether to withdraw the U.S. from the Paris climate accord.

That’s suddenly uncertain. Mr. Trump promised to withdraw during the presidential campaign, correctly arguing that the accord gave “foreign bureaucrats control over how much energy we use.” His transition team even explored strategies for short-cutting...