Step 1 : Introduction to the question "Who was the longest serving president, and the only one elected four times?"
...On this day in 1940, Franklin Delano Roosevelt, who first took office in 1933 as America’s 32nd president, was nominated for an unprecedented third term. Roosevelt, a Democrat, would eventually be elected to a record four terms in office, the only U.S. president to serve more than two terms. Roosevelt served as President between March 4, 1933 and April 12, 1945, a total of 4,422 days. FDR, as he was often called, led the United States through the Great Depression and World War II, and greatly expanding the powers of the federal government through a series of programs and reforms known as the New Deal.
Step 2 : Answer to the question "Who was the longest serving president, and the only one elected four times?"
Franklin D. Roosevelt:
Please let us know as comment, if the answer is not correct!