The result was a rushed and chaotic exit from the White House that is now at the center of a federal investigation into Mr. Trump’s handling of classified documents and other presidential material after leaving office.

“If you only start packing with two days left to go, you’re just running low on time,” a former aide said. “And if he’s the one just throwing things in boxes, who knows what could happen?”

Another former aide said uncertainty pervaded the West Wing in the final weeks as the president continued to contest the election. “It was a weird time,” the aide said. “It was like, are we doing this? Are we not doing this?”…

When John Kelly was chief of staff, the handling of classified and sensitive information in the White House alarmed him to such an extent that he sought to institute new protocols for the organization of such documents and for who was allowed to access them, Mr. Kelly said in an interview Saturday.

“It needed to be tightened up,” he said, adding that there was a lack of “deep understanding of the processes and procedures of security clearances and handling highly classified material.”