President Donald Trump with Federal Reserve Chairman Kevin Warsh at the White House in Washington, DC, on May 22. - Jonathan Ernst/Reuters/File

The Federal Reserve’s first rate hike in three years has ushered in a new twist to the already unusual relationship between President Donald Trump and the world’s most powerful central bank.

Trump raised eyebrows on Wednesday evening by appearing to suggest that he gave Kevin Warsh, his handpicked Fed chairman, permis...