What is Super Tuesday and why is it important? Here's what you need to know.

Fifteen contests will be held across the country.

There is no national primary voting day, but Super Tuesday is as close as it comes. The end of the day's voting will bring major delegate allocations and answer some of the questions looming over the Democratic primary.

Fifteen contests will be held across the nation on Tuesday. Polls close at various times beginning at 7 p.m. (EST) and extending until 11 p.m., though it is unlikely a winner will be projected in every state before the close of the night.

Here's what you need to know about the largest day of voting in primary season:

What states will vote on Super Tuesday?

AlabamaArkansas California Colorado MaineMassachusetts Minnesota North Carolina Oklahoma Tennessee TexasUtah Vermont

American Samoa will hold a caucus.

How important is Super Tuesday?

This is the first year that delegate-rich California will vote on Super Tuesday. Coupled with Texas, the two are by far the most delegate-heavy states.

Since his entrance into the race, former New York City Mayor Michael Bloomberg has had a laser-focus on Super Tuesday, pumping half a billion dollars into ads across the country. He has consistently risen in the polls, but Tuesday's ballots will be the first that feature his name.

Bloomberg's rise is accompanied by an influx of criticism of his past policies as a business executive and as mayor. His history with women, including a number of NDAs and controversial statements, has drawn heavy scrutiny from Democratic contenders who are also quick to highlight that until 2018, Bloomberg wasn't a registered Democrat.

Tuesday's contests will be a test of that defense.

Former Vice President Joe Biden will require a major showing to maintain his momentum out of South Carolina. Biden gained in the field after Saturday night's upset in South Carolina, and combined with the exit of former South Bend, Indiana, Mayor Pete Buttigieg, the entire Democratic field was re-calibrated ahead of the massive day of voting.

All of the candidates, save Sanders and Bloomberg, are increasingly strapped for cash, and Super Tuesday could be the last chance for some to buoy their candidacies through more contests down the line.

How many delegates are at stake?

About one-third of all pledged delegates will be doled out. Including the four early states, 40% of the total pledged delegates will be allocated by the end of the night.

The nominee will need to have a majority, or 1,991, of the pledged delegates at stake to nab the nomination come the convention this July in Wisconsin. On Super Tuesday, candidates will have had the chance to win 1,344 of those delegates across the 15 contests.

It's the amount of delegates, not the amount of votes, one receives that will put them closer to closing in on the nomination come July.

The nation is sure to get an answer on the contentious question of moderate versus progressive, and the race is likely to winnow after the massive day of voting.

What other races will Americans vote in?

There are a number of down-ballot races on Super Tuesday, including some high-profile primaries for candidates running for the Senate.

In Alabama, incumbent Democrat Sen. Doug Jones will likely carry the Democratic primary, though he will be vulnerable when it comes time for a general election in the Yellowhammer State.

Former Attorney General Jeff Sessions is in for a close race on the Republican side. While he is hoping to lean into his deep roots in the state, he is up against a challenge from two other formidable rivals: U.S. Rep. Bradley Byrne and former Auburn head football coach Tommy Tuberville. A candidate needs 50% of the vote to win the Republican nomination outright, but given the fractured primary, this race could go to a runoff.

In North Carolina, Democratic state Sen. Cal Cunningham is facing off with state Sen. Erica Smith for the chance to take on vulnerable Republican Sen. Thom Tillis. Allies of Senate Majority Leader Mitch McConnell have intervened in the race, creating a PAC which has backed ads supporting Smith, the more progressive candidate.

On the West Coast, the special election to fill the seat of former Rep. Katie Hill, who resigned from the House last fall after nude photos of her were leaked, will take place on Super Tuesday. The Democratic field is crowded for this seat, although Christy Smith appears to be the front-runner. Smith has nabbed endorsements from prominent Democrats, including House Speaker Nancy Pelosi, Sens. Diane Feinstein and Kamala Harris.

There are a number of primaries taking place in the Texas suburbs, an area to watch for the general election as well. The suburbs in the Lone Star State have trended blue in recent years, and former presidential candidate and Rep. Beto O'Rourke has stumped for many of the candidates on the ground.

These races will be yet another test of the moderate versus progressive factions of the party, and may temporarily answer existential questions regarding the future of the party.