WASHINGTON, Feb. 4 (Xinhua) -- The Super Tuesday in the presidential election year 2008 falls on Feb. 5 as 24 states and American Samoa are ready to elect their Democratic and/or Republican presidential candidates.

    The following is a brief introduction to Super Tuesday, the most important day in the U.S. presidential nomination race.

    Super Tuesday, or National Election Day, commonly refers to the Tuesday in early February or March of a presidential election year, when the largest number of states hold their primaries or caucuses, and elect delegates to a party's national nomination convention.

    The phrase of the "Super Tuesday" has been used since at least 1984. The particular states taking part in Super Tuesday have varied from year to year.

    In 2000, a total of 16 states held primaries on Super Tuesday, the largest presidential primary election day in U.S. history by then.

    Super Tuesday carries great weight because it involves many states from geographically and socially diverse regions of the country, and produce a huge chunk of delegates to the parties' nomination conventions, a key factor for winning the candidacy.

    Many U.S. states have moved up their primaries to Feb. 5, the Super Tuesday in 2008, bringing to 24 states and American Samoa the number of the total battlefields.

    In strong contrast with the "Mini Tuesday" in 2004 when only five states held primaries and two held caucuses, the 2008 "Super Tuesday" has been described by some media and pundits as "Tsunami Tuesday" considering its unprecedentedly wide participation.