Lame Duck Day is celebrated on February 6th of each year in remembrance of the Twentieth Amendment to the United States Constitution. The amendment reduced the amount of time between Election Day and the beginning of Presidential, Vice Presidential and Congressional terms. Originally, the terms of the President, the Vice President and the in-coming elected Congress began on March 4, four months after the elections were held. While this lapse was a practical necessity at the end of the 18th century, when any newly-elected official might require several months to put his affairs in order and then undertake an arduous journey from his home to the national capital, it eventually had the effect of impeding the functioning of government in the modern age.
From the early 19th century onward, it also meant that the lame duck Congress and/or Presidential administration could, as in the case of the Congress, convene or fail to convene; in the case of the administration, to act or to fail to act, or to meet significant national crises in a timely manner. Each institution could do this on the theory that at best, a lame duck Congress or administration had neither the time nor the mandate to tackle problems. Where as the incoming administration or Congress would have both the time, and a fresh electoral mandate, to examine and address the problems that the nation faced. These problems very likely would have been at the center of the debate of the just completed election cycle.
This dilemma was seen most notably in 1861 and 1933, as Abraham Lincoln and Franklin D. Roosevelt (plus the newly elected Members of Congress from the political party of each of these Presidents) had to wait four months before they, and the incoming-Congresses, could deal with the secession of Southern states and the Great Depression respectively.
Originally, under Article I, Section 4, Clause 2, the Congress was required to convene at least once each year in December. That requirement created a mandatory lame duck session following each federal election.
The amendment was ratified on January 23, 1933. Section 5 delayed Sections 1 and 2 taking effect until October 15, 1933. This delay resulted in the first meeting of the 73rd Congress, along with the inauguration of President Roosevelt and Vice President John Nance Garner, taking place on March 4, 1933.
On February 15, 1933, 23 days after this amendment was ratified, President-elect Franklin D. Roosevelt was the target of an unsuccessful assassination attempt by Giuseppe Zangara. If the attempt had been successful then, pursuant to Section 3, John Nance Garner would have been sworn in as President on March 4, 1933.
The first Congressional terms to begin under Section 1 were those of the 74th Congress, on January 3, 1935. The first Presidential and Vice Presidential terms to begin under Section 1 were those of President Roosevelt and Vice President Garner, on January 20, 1937.
Because of this amendment, if the Electoral College fails to resolve who will be the President or Vice President, the newly elected Congress, as opposed to the outgoing one, would choose who would occupy the unresolved office or offices.