Vermont Sen. Bernie Sanders’ quest for the Democratic presidential nomination has a problem. Actually, it has a number of issues: party elites aren’t endorsing the candidate, he has limited support outside his Vermont-style white liberal base, he showed some support for Second Amendment rights in a party that tends to push gun control, and he’s not even a Democrat – he's an Independent. I could go on, but one specific problem threatens to stop Sanders’ building momentum in its tracks. That problem is Super Tuesday.

What is Super Tuesday?

Super Tuesday is a presidential primary tradition, a Tuesday in Feburary or March when a number of states simultaneously hold their primary contests. These contests typically signal a new stage in the primary.

Before Super Tuesday, only a few smaller states hold contests – next year it looks like Iowa, New Hampshire, Nevada and South Carolina will – and those contests give lesser-known, underfunded candidates a chance to prove themselves and thus gain media attention, build a national profile and raise the money necessary to make a credible run at their party’s nomination.

On Super Tuesday, the presidential primary goes national. Candidates are forced to compete in a large number of states at the same time – which means their organizations have to be able to mobilize supporters, buy ads, get their messages out and ultimately win contests on a much larger playing field. Candidates who fare poorly on Super Tuesday, like those who fail to gain traction in early primary states, often realize they have little chance at winning their party’s nomination and drop out.

Why Is Super Tuesday Bad for Bernie?

As other analysts have pointed out, the first two nominating contests – Iowa and New Hampshire – feel like home to Sanders. He hails from Vermont, one of the whitest and most liberal states in the country. The Democratic primary electorates in both of these states happen to be pretty liberal and white, giving the Vermonter an opening to do well in (or maybe even win) those primaries.

But Sanders’ luck might run out quickly after those early contests.

Each point in this graph represents a state. Each point's size is proportional to the number of delegates that state is allowed to send to the Democratic presidential nominating convention, and the states that are higher on the vertical axis have a higher percentage of white and liberal voters. The red line is a local regression that shows approximately how white and liberal the Democratic electorate is at that time in the primary.

The pattern here is pretty clear – Sanders is in friendly territory for the first two primaries, but the downward trend is steep and hits a low point on Super Tuesday. The primaries are a bit more white and liberal after Super Tuesday, and data is missing for a few potentially Sanders-friendly states (e.g. Maine and Washington), but it could be tough for Sanders to recover from the resounding losses he might suffer throughout March. That’s because donors, activists and primary voters like to support candidates who both share their beliefs and can win the general election. If Sanders performs poorly on Super Tuesday, he could lose any aura of electability that he gained by doing well in early contests.

(Note: We borrowed our measure of how white and liberal a state is directly from Nate Silver at FiveThirtyEight. He multiplied the white percentage of the vote by the liberal percentage in the 2008 primaries using exit poll data – which was available for most but not all states. The primary dates and delegate counts are subject to change. Our data on that are taken from The Green Papers.)

But why is Super Tuesday so much worse for Sanders than other big days in the Democratic primary calendar? Larry Sabato, Kyle Kondik and Geoffrey Skelley presented an answer while making some similar arguments about Sanders and the primary calendar at Sabato’s Crystal Ball. They cited a number of factors, one of which was Clinton-friendly demographics.

To see this, take a look at the blue states in the following map – those are the states currently scheduled to hold primaries on Super Tuesday.

Sabato, Kondik and Skelley point out that the Democratic Party in many of these Southern states is heavily African-American or Hispanic. Both of these constituencies are, for now, firmly in Clinton’s camp.

Some of these states are favorable for Sanders. Vermont is his home state, and Massachusetts has a relatively high concentration of white liberals. Additionally, Minnesota and Colorado show potential for Sanders. Then-Senator Obama beat Clinton in both states by over 30 points in the 2008 Democratic primary, and neither state has a high concentration of African-Americans – meaning that a good portion of Obama’s strength likely came from white liberal voters who might support Sanders.

That being said, Clinton’s advantage is big on Super Tuesday. More states favor her, and those states send more delegates to the Democratic National Convention. Texas alone has more delegates than Colorado, Minnesota and Vermont combined. So even if Sanders scores a few wins on Super Tuesday, he is, on the whole, in unfriendly territory.

One of Many Scenarios

While Super Tuesday is one plausible end to Sanders’ campaign, there are a number of reasons it could turn out differently.

First, the primary calendar is not completely set. It is still possible for states to shift their primaries in a way that changes the dynamics of the primary.

Second, Sanders might lose before Super Tuesday. It’s possible that he flounders in a debate or suffers a big loss in one or both of the two early states. Maybe one of the other less-than-electable leftist Clinton alternatives will catch fire and eclipse him. There are a lot of different ways the Democratic primary could pan out, and not all of them end in Clinton clinching the nomination by beating Sanders on March 1.

Third, expectations matter. Even if Clinton beats Sanders by significant margins on Super Tuesday, he could still outperform expectations and thus gain the media attention and money needed to survive. And (in a less likely but much worse scenario for Clinton) if she loses both Iowa and New Hampshire, goes on to underperform expectations on Super Tuesday and starts to lose the confidence of the party elite, then the primary could become longer and much more competitive than the Clinton campaign would like. Alternatively, Sanders could raise expectations in early states, not quite meet those expectations and thus face an earlier end than he would like. So simple wins and losses are not the only factors that matter here – candidates and we in the media set expectations prior to primary elections, and those expectations partially dictate how much or little momentum a candidate gains or loses from a victory or a defeat.

Fourth, Sanders could theoretically increase the breadth of his appeal. If he somehow manages to broaden his appeal beyond white liberals, he might make a real run at the nomination. This seems unlikely – Sanders is quite liberal and thus might have trouble appealing to the more moderate portions of the party. Clinton managed to hold onto Hispanics in 2008 despite a strong challenge from then-Senator Barack Obama, so she is unlikely to lose their support to a weaker opponent like Sanders. Sanders recently began courting African-American voters – another key part of Clinton’s coalition. While Sanders could highlight his liberal policy positions and history with the civil rights movement, he faces an opponent who has deep, longstanding connections to the African-American community – and who didn’t recently botch a response to Black Lives Matter protestors.

I could list more caveats, but the point is clear – there are a number of possible paths and strategies that Sanders could take in the Democratic primary. In my view almost no scenario ends in him actually winning the nomination, but a number of realistic possible paths lead to the end of his campaign in early March.