Super Tuesday is make or break for Bernie Sanders. Here are the key states to watch.

There are two big questions to keep in mind when looking at the results from the 11 states voting in the Democratic primary contest on Super Tuesday.

One is quite literally whether Hillary Clinton or Bernie Sanders gets closer to amassing the number of delegates necessary to win the campaign. The first candidate to rack up 2,382 delegates secures the Democratic nomination, and 865 of them are up for grabs on Tuesday.

Right now, it looks like Clinton could rack up around 200 more delegates tomorrow than Sanders. Much of the voting happens in the South, where Clinton has had large polling leads, and her overwhelming victory in South Carolina on Saturday — powered by an 87-13 margin among black voters — suggests she should end Tuesday night with an even bigger delegate lead.

A separate question to consider is what the results tell us about the rest of the primary. The 11 states voting on Tuesday have important demographic differences from the ones that lie ahead, and Sanders could be encouraged by tomorrow's outcome while still falling behind in both the delegate total and the number of states won.

For that to happen, Sanders needs to start taking states outside of the Northeast. Most observers we spoke to think that if Sanders can't win Minnesota and Colorado and at least put up a fight in Oklahoma and Tennessee on Tuesday, his campaign is probably toast.

But if Sanders defies current polling and pulls off a surprising sweep outside of Clinton's Southern stronghold, we'll likely be looking at a long and drawn-out race for the Democratic nomination.

What will the state-by-state results on Tuesday tell us about the national race?

Here's an inexact way to divide the 11 states that will be voting in the Democratic nomination on Super Tuesday into three basic groups:

• Five Southern states — Alabama, Georgia, Texas, Arkansas, and Virginia — that are expected to be safely in Clinton's camp. A Sanders win in any of these primaries would represent a huge upset, but he can lose them — even by significant margins — and still have a viable path forward.
• Four states that Sanders will probably need to win — Vermont, Minnesota, Colorado, and Massachusetts — to have a shot at the nomination. If Sanders can't sweep these primaries, he's unlikely to have a credible case for how he can mount a serious campaign. (A recent poll put Clinton up in Massachusetts, a result that would be disastrous for Sanders's chances.)
• Two states — Oklahoma and Tennessee — that will test a major part of Sanders's coalition: Sanders has done well with the white working class in the early primaries, but it's unclear if that will extend beyond Iowa and New Hampshire. FiveThirtyEight's Nate Silver projects that Sanders probably needs to do well in places like Oklahoma and Tennessee to win the nomination, but they're not as likely to be in his corner as the four states above.

The Super Tuesday terrain is more favorable to Clinton

Estimates vary, but Clinton could expect to get at least 175 more delegates than Sanders on Tuesday, said Richard Berg-Andersson, researcher at the Green Papers, which tracks delegate math closely.

"That would be a good night for her, a decent night, what you'd expect," Berg-Andersson said. "If you start going below a 100-delegate difference between them, or if it's, like, 50 or if Sanders is ahead, that would be a disaster for Hillary Clinton."

Hillary Clinton at a rally in Nevada in October 2015. (Frederic J. Brown/AFP/Getty)

Of the 865 available delegates on the table, Clinton should end the night by taking somewhere around 550 of them. Sanders's delegate target for Tuesday is probably closer to 400.

How much of the raw vote could Sanders lose by and still feel decent about his chances? Josh Putnam, a political scientist at the University of Georgia, said Sanders could lose by a 52-48 margin across the Super Tuesday slate and still feel upbeat.

"That's a huge win for Sanders," Putnam said about the hypothetical 52-48 finish. "He's losing, yes, but it's a win relative to expectations ... and this is an area of the South where Clinton was expected to do very well. That would project a much longer and pitched battle between them for the rest of the primary calendar."

On the other side, having Clinton win closer to 60 percent of the popular vote across the Super Tuesday states would be a sign of major trouble for Sanders, according to Putnam. And she could definitely do so, given what polls have suggested about her support among African-American voters and given the overwhelming victory she had in South Carolina.

Still, if Sanders can avoid getting blown out in the South on Tuesday, Putnam said, he'll have one other reason to be optimistic for his long-term chances: the strange Democratic delegate math.

How to make sense of the Super Tuesday delegate math

The Democratic nomination does not just come down to which candidate gets the most votes. That's in part because of the 4,763 delegates who vote at the Democratic convention, 712 of them are "superdelegates" — party elites and other insiders chosen by the Democratic National Convention who get to back whichever candidate they prefer.

A banner at a Sanders rally in Nevada. (Ethan Miller/Getty)

But even the other delegates — the ones chosen by the voters — have special rules that may complicate the relationship between the popular vote and the outcome.

Only about a quarter of delegates are allotted by the statewide results. The other three-quarters are allotted proportionally by vote totals in various districts, typically determined by congressional districts.

Each district gets a certain number of delegates to apportion. The challenge is that many of them have an even number of delegates, and the Democrats' rules make it very difficult for any candidate in a close two-way race to do anything more than split the district's delegates evenly.

In fact, it takes winning more than 62.5 percent of the vote total to do more than split a district's delegates, according to Elaine C. Kamarck, senior fellow and director of the Center for Effective Public Management at the Brookings Institution. That means in a district with four delegates, the vote total could be 61 to 39 and both candidates would each get two delegates.

Clinton at a rally in New Hampshire. (Scott Eisen/Getty Images)

In other words, a candidate can win dozens of districts by thousands and thousands of votes and have no advantage among the delegates to show for it. Someone can remain relatively close in the delegate count even while getting soundly beat in vote totals. A candidate needs to win in a landslide to clean up in delegates.

"On the Democratic side, the mathematics favor the losers, not the winners," said Kamarck, who is also the author of a book called Primary Politics.

Why this weird delegate math may make life difficult for Sanders

This is one of the reasons Tuesday could prove so crucial: The difficulty of clean delegate wins makes it very difficult for candidates to come back after falling behind.

By the end of Super Tuesday, around one-quarter of Democratic delegates will have been awarded. If Clinton breaks out a delegate lead with big wins in the South, Sanders will find it very challenging to find places where he can make a comeback.

"Anything as small as a 100-delegate lead will be very difficult for Sanders to crack into, to chip away at," Putnam said.

In 2008, Barack Obama won 11 consecutive states that gave him an essentially insurmountable delegate advantage over Clinton, according to Putnam. "He only had a modest delegate lead, but she found it very difficult to get back into it because of the proportional rules," Putnam said.

This could work against Sanders if he gets clobbered across the South on Super Tuesday. But it could also help him: If he hangs tough in the South, Sanders may be able to run up the delegate score in the Northeast and in the caucus states, where he's expected to do better.

Some candidates have been better at thinking through the implications of these rules than others.

For instance, Clinton beat Obama in 2008 by a big margin in New York, where she had served as senator. But Obama successfully targeted several districts within the state with disproportionately large numbers of African-American voters, thus minimizing his delegate losses in New York, according to Kamarck.

"Obama got a very respectable number of delegates out of New York, even though Hillary had a substantial win in that state," she said. "So while the statewide wins matter for momentum and publicity, it's actually the district-by-district wins that maters more."

The map gets better for Sanders after March 1, but not by much

The problem is that none of this will matter if Sanders performs as poorly as many of the recent state polls have suggested.

Sanders's supporters have largely pointed to national polls as evidence that he's drawing closer to Clinton. At the same time, Sanders has trailed by double digits in a number of state results — including one that showed Clinton actually running ahead of Sanders in Massachusetts.

"The state polls end up being more accurate at this point in the race," Putnam said. "We don't have a national primary, and the national polls tend to lag rather than lead. ... The state level polls are the ones that are picking up on changes, to the extent they exist."

The Democratic presidential candidates debate in New Hampshire. (Justin Sullivan/Getty Images)

If Sanders loses big on Super Tuesday, the map does begin to look better for him, but only in the long run. The next three states are Louisiana, Nebraska, and Kansas — not exactly states with his prime constituency. Contests then move to Maine and Michigan — states that theoretically should look good for Sanders (although one recent poll put Clinton up by 39 points in Michigan).

Sanders probably has raised enough money to remain in the race for the long haul, even if he gets trounced on Super Tuesday. But by most other metrics — statewide polling, endorsements, superdelegates — Clinton appears to be in a formidable position to effectively wrap up the nomination well before the convention.

"Folks in those positions just don't lose very often," Putnam said.

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