At around noon on Jan. 20, Donald J. Trump will once again stand outside the U.S. Capitol, place his hand on a Bible and recite the oath of office, this time becoming the 47th president of the United States. His remarkable comeback, punctuated by a resounding electoral victory on Nov. 5, marks the first time in 132 years a former president reclaimed the White House after a term away. But as the 78-year-old Republican prepares to lead a deeply divided nation, all eyes are on the critical decisions shaping his second-term agenda—starting with the assembly of a cabinet and the rollout of aggressive trade policies toward China.