What is Super Tuesday and why is it important?

What happens on Super Tuesday will shed some light on the big questions around the Democratic presidential primary - and there are a lot more questions than usual at this point in an election cycle.

Here's what you should know.

Q: When is Super Tuesday?

A: It's March 3. It will be the first big primary day after the four early nominating states - Iowa, New Hampshire, Nevada and South Carolina - hold their votes.

Poll closing times vary by state: Vermont's close first at 7 p.m. Eastern, and California's last at 11 p.m. Eastern. We won't know all the results Tuesday, since tabulating votes could go late into the night, especially on the West Coast. California's results will take days, at least, as mail-in ballots must be postmarked by election day.

Super Tuesday is a popular day to hold a primary because so many states want an early say in who gets the nomination. So they've clustered as early as they can without stealing any thunder from the first four states, which have deals with the Democratic National Committee to go in the order they do.

(Republicans also can vote in their presidential primaries in most Super Tuesday states, but since President Trump doesn't face a serious challenger we're focusing here on the Democrats.)

Super Tuesday is relatively early in the primary process; there will be Democratic primaries and caucuses happening all the way until June.

Q: Which states are voting on Super Tuesday and how many delegates are at stake?

A: Fourteen states and one U.S. territory will hold nominating contests on Super Tuesday, to award a total of 1,357 delegates.

The states are across the country - literally from California to Maine - and include heavily Democratic Massachusetts, traditionally Republican Texas and Oklahoma and more in-between states like Colorado, North Carolina and Virginia. Democrats who live in American Samoa will also caucus on Super Tuesday, and Democrats who live abroad will begin casting ballots.

Let's step back for a moment to explain that it's the delegate total, not the sheer number of votes, that counts when figuring out who wins a party's presidential nomination. Each state is allotted a certain number of delegates based on a formula of population and weight in the Democratic Party. The state parties then award delegates to the candidates based on the votes they receive. The first candidate to get a majority of the nearly 4,000 delegates wins the nomination.

This year, Super Tuesday is even more consequential because California moved its primary up to March 3. It had been voting in June, at the tail end of the nominating process when there's typically less at stake. The addition of the most populous state adds even more heft to Super Tuesday; 30 percent of the delegates awarded on Super Tuesday will come from California.

No one can win the nomination on Super Tuesday alone, but doing well that day can get you a long way toward winning a majority of the 3,979 delegates up for grabs. Thirty-four percent of delegates are offered on Tuesday. That's more than any other single day in the nominating contest.

Before Super Tuesday, less than 5 percent of delegates will have been allotted. After: 38 percent.

Q: Why is Super Tuesday important, especially this year?

A: Heading into Super Tuesday, the race for the Democratic nomination is still wide open. Sen. Bernie Sanders of Vermont and former South Bend, Indiana, mayor Pete Buttigieg have finished in the top two in both Iowa and New Hampshire, and Sanders is leading recent national polling. But no state contest has presented a potential shake-up like the one this Super Tuesday could provide.

The Democratic field is still relatively big, with eight candidates. It's possible some candidates will drop out if they don't perform well in Nevada and South Carolina, but if not, Super Tuesday could serve to winnow the field. 

The first four nominating contests in February happen about once a week, with candidates building off momentum from one contest to the next - or weighted down by a poor performance.

But with 14 states voting all at once, Super Tuesday could serve as more of a gut-check for where the Democratic Party electorate is. Voters across the country will go to the polls with the race still in flux. Super Tuesday also offers a big contrast to the early states, particularly Iowa and New Hampshire, by allowing Democratic voters from politically and demographically diverse regions chime in.

There's another reason Super Tuesday could have an especially big impact this year: Former New York mayor Mike Bloomberg will first appear on presidential ballots then. He entered the race late, skipped the early states and has spent some $350 million of his own money on campaign ads, and his standing in the polls, including among black voters, has risen as former vice president Joe Biden's has slipped.

- What to watch for ahead of Super Tuesday:

1. How does Bloomberg do on the ballot? It's the first time he'll be on, due to his novel strategy of skipping the early states. He's got momentum, from what we can tell from early state polls. But that rise is coming with increased scrutiny of his racially divisive policies as mayor and history of crude comments to women and gender-discrimination lawsuits at the company he runs. His first test will come on the debate stage on Wednesday in Nevada, even though he's not on the ballot there.

2. Do Biden and Sen. Elizabeth Warren, D-Mass., survive beyond Super Tuesday?

These high-profile candidates had disappointing showings in Iowa and New Hampshire. Biden's supposed firewall is with voters of color in Nevada and South Carolina, the last two elections before Super Tuesday. Warren's campaign warns this is a long campaign and has looked to Super Tuesday states for a strong showing. (Her home state of Massachusetts will be voting and she hopes to come in the top two in many others.) But what happens if they don't do as well as they hoped? How do they make the case to donors if such a wide swath of voters chimed in and didn't support them?

3. Does Super Tuesday blunt Sanders' momentum in any way? Since the Iowa caucuses, Sanders has been leading in national polls. But some polls in Super Tuesday states show he's bunched up with other candidates, like Biden and Warren and Bloomberg. Sanders still has plenty of convincing to do within the Democratic establishment that he can beat Trump, and finishing outside the top three in a significant number of Super Tuesday states could seriously ding his argument that he can win a national election.

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Super Tuesday as we know it was born out of a desire by Democrats in the 1980s to nominate a more moderate candidate, said Richard Berg-Andersson, an elections expert with The Green Papers blog. In 1984, Democrats nominated Walter Mondale, who got crushed in the general election by Ronald Reagan. So for the next election, the Democratic Party in Southern states moved their primaries en masse to March to try to have the more conservative wing of their party chime in sooner in the hopes of boosting a more moderate candidate. (It didn't really work: Democrats nominated then-Massachusetts Gov. Michael Dukakis who was perceived to be more liberal than Southern Democrats wanted, Berg-Andersson said in an email.)

Today, Super Tuesday is more geographically diverse and less about specific regions trying to influence the election. Rather, each state wants a say earlier and earlier and earlier in the nominating contest, for fear of being left out of the decision-making. It takes some the fun out of picking if you already know who your nominee will be. Super Tuesday has swollen so much that during the 2008 election for both Democrats and Republicans, about half the states had their contests on one day.

Super Tuesdays can be decisive and signal the end of a primary, like it was for both parties in 2000, said Josh Putnam, a political science professor who runs the elections blog Frontloading HQ. "But they can also show whether things are evenly divided or evenly enough to keep primary season going for a longer time," he said in an email.