(This Amendment is rather lengthy, but basically sets the commencement date of the terms of the President, Vice-President and Members of Congress.”)
The 20th Amendment is referred to as the “Lame Duck Amendment”, so called because an elected official who has not been reelected still retains office. The 20th Amendment’s purpose was to shorten the “dead time” between elections and the date someone actually took office. Originally, the inauguration date for the President, for instance, was March 4 – when the election actually took place the previous November – so the 20th Amendment voided the time in office with diminished power.
When the Constitution was written, there was a long time interval between elections and taking office because of the time it took back then for communication and travel. It took days and weeks for We, the People to find out who actually won an election and weeks or months for the newly elected person to get to the Capital. In those days, holding office was considered a part-time occupation, and it took some time for newly elected representatives to get their businesses and affairs in order and make their way to their new office, so the March 4 date made some sense.
But the March 4 date also brought about an unacceptable legislative condition: it was physically impossible to give appropriate attention to the nation’s business in the way of researching and approving important legislation in that short time span. The result was important issues got backlogged and a significant log jam was created. So the 20th Amendment tried to avoid the time in office with diminished power by abolishing to a large extent the “short session” of Congress.
The other interesting aspect of the “old system” is that if a President did not get a majority of the electoral votes, the November election of the President would be determined by the membership of the “old” House of Representatives rather than the “new” House just elected by the people. The situation could manifest where the “old” members who just were thrown out of office by the people and might be a little bitter, would choose the next President who would be in control for the next 4 years.
This actually occurred when outgoing President John Adams set the stage for the Marbury v. Madison landmark Supreme Court decision by his late-night, last-minute appointments before he walked out the door.
Bill Clinton got to dodge the impeachment bullet in 1998 because the final House vote to impeach occurred after the 1998 elections, and the Senate was not scheduled to hear the case until the new Congress was sworn in the following January. Arguments that the 20th Amendment conceptually required a revote by the NEW House did not pick up any momentum and the issue died.