Super Tuesday 2008,^[1] Super Duper Tuesday,^[2][3][4][5] Mega Tuesday,^[6] Giga Tuesday,^[7] Tsunami Tuesday,^[8] and The Tuesday of Destiny^[9] are names for February 5, 2008, the day on which the largest simultaneous number of state U.S. presidential primary elections in the history of U.S. primaries were held.^[10] Twenty-four states and American Samoa held either caucuses or primary elections for one or both parties on this date.^[11] Furthermore, the week-long Democrats Abroad Global Primary began on this day.

The large number of states that held elections on February 5 could have shortened the period between the first caucus in Iowa, on January 3, 2008, and the de facto selection of a party's nominee to just a few weeks.^[2] Super Tuesday 2008 saw 52% of the Democratic and 41% of the Republican delegates awarded by early February 2008. By comparison, only about 1% of nominating convention delegates had been selected by that point in the 2000 election cycle.^[12][13] It was held approximately one month before Super Tuesday II.

The name "Super Duper Tuesday" is a reference to earlier Super Tuesdays, the dates on which the largest number of presidential primaries took place. The term "Super Duper Tuesday" has been repeatedly re-coined to refer to even more states holding their primaries on this date, with the first recorded usage so far found dating back to 1985.^[14] In 2004, Super Tuesday fell on March 2.^[2] In 2004, the equivalent cohort of primaries, on February 3, 2004, was called "Mini-Tuesday"—only seven states held their primaries on that date.

On June 3, 2007, the name "Tsunami Tuesday"—conveying the potential of the large number of simultaneous primaries to completely change the political landscape—was mentioned^{[by whom?]} on Meet the Press during a round-table discussion with presidential campaign strategists James Carville, Bob Shrum, Mary Matalin, and Mike Murphy.

Super Tuesday in 2008 occurred during Mardi Gras and on the day of the New York Giants Super Bowl victory parade. Voting was hampered in several states by a major tornado outbreak that killed 57 people, and competed with the primaries for the news. (Due to such influence, the outbreak was named^{[by whom?]} after the primaries.)^[15]

This article contains weasel words: vague phrasing that often accompanies biased or unverifiable information. (March 2009)

As of February 2007, eight states planned to hold primary or caucus elections on Super Tuesday, February 5, 2008: Alabama, Arkansas, Delaware, Missouri, New Mexico Democrats, North Dakota, Oklahoma, Utah, and West Virginia Republicans^‡.^[2][3] However to increase their importance in the candidate selection process, several states moved up their contests, which some pundits criticized as being "pure self-interest."^[10]

The following states changed their elections to February 5: Alaska,^[16] Arizona,^[17][18] California,^[3] Colorado,^[17] Connecticut,^[19] Georgia,^[16] Idaho Democrats,^[20] Illinois,^[4] Kansas Democrats^†,^[21] Massachusetts,^[22][23] Minnesota,^[5] Montana Republicans^§,^[24] New Jersey,^[25] New York,^[26] and Tennessee.^[27]

In an attempt to keep states from moving their primary or caucus elections even earlier, the Democratic National Committee and Republican National Committee established penalties for states holding elections earlier than February 5, 2008.^[12] As a result, the Democratic National Committee controversially stripped the states of Michigan and Florida of all pledged convention delegates.^[28] The Republican National Committee has reduced by half the number of convention delegates from five states: Wyoming, New Hampshire, South Carolina, Florida, and Michigan.^[29]

• Mini-Tuesday
• Super Tuesday
• Super Tuesday II, 2008
• 2008 Super Tuesday tornado outbreak

• The New Mexico Democratic Caucus came down to provisional ballots. The counting process took 9 days to complete.
• † The Kansas state legislature voted to neither fund nor hold a primary in 2008.^[21]
• ‡ West Virginia Republicans will select 18 of their 30 delegates on February 5, with the final 12 chosen on May 13.^[21]
• § Montana Republicans chose to select delegates using a "closed caucus" comprising approximately 3,000 Republican elected officials and state party officials, such as precinct captains.^[24]
• ¤ American Samoa is an unincorporated territory of the United States with three delegates to the Democratic National Convention, but no vote in the presidential election.
• (C) denotes states and territories holding caucuses.
• (WTA) means Winner Takes All, and applies solely to Republican contests.

Popular Vote Percentages reflect the percentage within each party, not state overall total votes cast.