In 1952 President Harry Truman started a tradition of providing presidential nominees with classified briefings. Many attribute this decision to Truman’s experience ascending to the presidency. In 1945, he had been vice president for just 82 days before then-President Franklin D. Roosevelt died.
Truman assumed the mantle of Commander-in-Chief of the United States during WWII and was quickly made aware of the well-kept secret of the nation’s atomic bomb capabilities.
According to NPR’s Mary Louise Kelly, “Truman had made up his mind that his successor should assume the Oval Office better prepared than he had been, so he offered classified briefings to each of the nominees, a tradition that’s held ever since.”
The sitting President determines who receives clearance to obtain classified national security information.