When: Tuesday, March 3. Balloting will occur in 4 U.S. time zones, plus American Samoa and Democratic ex-pats scattered all over the world. (Democrats Abroad vote from March 3-10)

Which states vote on Super Tuesday?

Alabama

Arkansas

California

Colorado

Maine

Massachusetts

Minnesota

North Carolina

Oklahoma

Tennessee

Texas

Utah

Vermont

Virginia

The states casting ballots on Super Tuesday together comprise 40% of the U.S. population. Democrats Abroad and American Samoans (the latter of whom do not get to vote in the general election) also vote. And Republican primary voters cast ballots in all states but Virginia, where the state Republican Party canceled its primary election to throw delegate support behind the incumbent, President Donald Trump.

How: It varies by state. Most have in-person balloting, but Colorado is entirely vote-by-mail, and California allows people to vote by mail if they wish.

Super Tuesday is considered the big prize in the presidential nominating process, a big election day that makes expensive and time-consuming demands of candidates who must appeal to voters from the northeast tip of Maine to the southwest corner of California. It's an election day that includes wide swaths of the American electorate, both geographically and demographically, and requires candidates to make pitches to such diverse interests as Minnesota farmers, California tech-sector workers and federal employees in Virginia.

This year, Super Tuesday is especially super, as California moved up its primary to join the pack. With electoral behemoth Texas also voting March 3, a big chunk – 1,357 – of the Democrats' 3,979 pledged delegates are at stake. A candidate must win more than half of the 3,979 delegates, or 1,991 delegates, to secure the Democratic nomination before the convention.

Super Tuesday has roots going back to 1984, but became a single-day force in 1988, when Southern states banded together to counter what some had critically dubbed the "Iowa syndrome," whereby a small Midwestern state had amplified power as the first nominating contest. If the South couldn't be first, it could be the biggest, the theory was, and candidates would need to spend time there addressing concerns of Southern voters.

The delegate haul also holds the promise of elevating a particular candidate, or forcing one or more out of the race. Bill Clinton in 1992 gained critical momentum in that year's Super Tuesday (despite not prevailing in either Iowa or New Hampshire) and went on to get the Democratic nomination and the presidency. But the path is not always so clear, and a Super Tuesday-heavy strategy can go terribly wrong.

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In 2008, for example, many states were grumbling about being ignored by presidential candidates who focused much of their attention on early states. In some cases, a presidential nomination is all but decided by early spring, leaving later states with no leverage in getting candidates to address issues important to those states' voters.

Michigan and Florida upped the ante, violating DNC rules to move their own contests to two January dates – after Iowa and New Hampshire but ahead of that year's Feb. 5 Super Tuesday (both states then had delegate fights with the national party at the convention). And a record 24 states, representing more than half of pledged delegates, held their primaries on Super Tuesday in 2008.

But that day didn't determine the Democratic nomination, which was closely fought by Barack Obama and Hillary Clinton. Since Democratic primaries and caucuses award delegates proportionally, and not as the winner-take-all contests employed by the Republican Party, both candidates stayed competitive in a race that wasn't decided until June of that year.

Ironically, the rush to be early backfired that year, and later states, such as Pennsylvania, Indiana and Oregon, became more critical. Even Puerto Rico – which is allowed to cast ballots in primaries but not general elections – saw visits from Obama and Clinton, as it appeared the Caribbean island might put one or the other over the top in the delegate race.

This year's Super Tuesday is expected to winnow the field more, if only because there are so many more viable candidates in the race, several of whom have overlapping bases of support.

A new wrinkle in the 2020 race is former New York City Mayor Mike Bloomberg , who got into the race late (November 2019) and made it a deliberate strategy to skip the first four nominating contests in the hopes of making a big splash Super Tuesday. With an estimated fortune of $60 billion , Bloomberg is self-funding his campaign and has been flooding the airwaves with professionally-produced ads, helping to propel him in national and state polls.

That sort of strategy would likely be politically suicidal for someone without a massive bank account to pull off, since success in early states brings in donations. But since Bloomberg doesn't need anyone else's money, the dynamics are radically different. A strong showing by Bloomberg Super Tuesday would dramatically – and perhaps permanently – change the rules of the game for future presidential elections.

Who is on the ballots in Super Tuesday states?

These candidates are on the ballot in every Super Tuesday state:

Former Vice President Joe Biden

Former New York City Mayor Mike Bloomberg

Rep. Tulsi Gabbard of Hawaii

Sen. Bernie Sanders of Vermont

Sen. Elizabeth Warren of Massachusetts

Former South Bend, Indiana Mayor Pete Buttigieg, Sen. Amy Klobuchar of Minnesota and Businessman Tom Steyer all made the ballots in each state but dropped out after the South Carolina primary.

Some ballots have more candidates and some ballots have other candidates who have already suspended their campaigns.

No matter who they choose, these primary voters hold an important place in the election process. Here’s a picture of who those voters are, according to data from USAFacts.

Which of the Super Tuesday states have the highest voting rate?