At first glance, South Carolina looks like the place where the more traditional candidates should win and recover from the victories of Bernie Sanders and Donald Trump in New Hampshire.
George W. Bush (2000) and John McCain (2008) essentially sealed their GOP nominations by defeating insurgent candidates in South Carolina. Hillary Clinton is expected to have a huge advantage there because South Carolina has a very large black population (28%), with more than half the voters in the Feb. 27 primary expected to be African-American.
But a closer look suggests that Sanders and Trump could win this state, and that none of the candidates in either party should consider it a lock. (South Carolina Republicans will vote on Feb. 20, a week earlier than Democrats.)
Here are some of the key voting blocs to watch:
1. Blacks Under Age 45 (25 percent of the Democratic primary vote in 2008)
African-Americans are a kind of outlier in modern politics. They disproportionately attend church weekly and often describe their political ideologies as conservative, two factors that generally associate with supporting Republican candidates. Instead, about 90 percent of blacks vote for the Democratic candidate in presidential elections.
Moderate political views and regular church-going would suggest Clinton will have an advantage with African-Americans. In national polls, Sanders tends to draw support from more secular and liberal Democrats, while more religious and moderate Democrats back Clinton.(To be sure, in New Hampshire, Sanders won moderates and all age groups except those over age 65, who favored Clinton.)
Combine those two factors with Clinton's advantage among older Democrats, and it's hard to see the Vermont senator making many gains among blacks over age 45.
But if Sanders is going to win the Democratic nomination, he will need support from people of color. So younger African-Americans (those 45 and under) in South Carolina are an important test for his campaign.
And there may be an opening for Sanders to appeal to young blacks as a more progressive candidate than Clinton on racial issues, as the senator has already done on the economy.
The black activism of the last two years has been the kind of political revolution that Sanders says his presidency could be, and the activists behind Black Lives Matter and the Sanders' campaign share disdain for what they describe as the political establishment.
There is a young cohort of African-American leaders and activists, including those involved in BLM, who feel pride in President Obama's achievements but are calling for more aggressive policies on issues like policing. Some of these young blacks are already backing Sanders, such as former NAACP president Ben Jealous (who is 43), the award-winning writer Ta-Nehisi Coates (40) and civil rights attorney and South Carolina state representative Justin Bamberg, who is 28.
Another potential advantage for Sanders is that young black voters are unlikely to have voted for either Bill Clinton (many were too young to cast ballots in 1992 and 1996) or Hillary Clinton (they overwhelmingly supported Obama in 2008).
But making these gains among blacks will not be easy for Sanders. Clinton has many more endorsements from influential black activists, both younger and older, than the Vermont senator.
And Obama, who remains very popular among black voters of all ages, has all but endorsed the former secretary of state. Clinton's official Twitter account recently posted the 2013 video from Clinton and Obama's joint "60 Minutes" appearance, when the president dubbed her "one of the finest secretary of states we've had."
If Clinton wins overwhelmingly wins young black voters in South Carolina, it will help her beat back the idea that Sanders is the candidate of young people. Of the Americans born between 1982 and 2000, what is known as the millennial generation, 44% are minorities, according to census data. A candidate who is winning only white young voters is appealing to only a slice of the millennial electorate.
2. South Carolina's Republican Moderates and "Somewhat Conservative" voters (64 percent of the GOP vote in 2012)
In recent South Carolina presidential primaries, about a third of the GOP voters there have described themselves as "moderate or liberal," and another third cast themselves as "somewhat conservative." (The other third is "very conservative" voters.)
That more moderate vote is expected to be particularly large around Columbia, the state's capital, and in the Charleston area. Mitt Romney won some of the counties around those cities in 2012, even as Newt Gingrich won the state.
The results in the early states in 2016 and in previous primaries suggest that these more moderate voters are likely to be resistant to a very conservative and religious candidate like Texas Sen. Ted Cruz. So this is a huge bloc of potential voters for ex-Florida Gov. Jeb Bush, Ohio Gov. John Kasich, Florida Sen. Marco Rubio and Trump.
In Iowa, moderate and somewhat conservative voters preferred Trump and Rubio over Cruz, a pattern that was repeated in New Hampshire, with Trump and Kasich outperforming Cruz among those blocs.
3. South Carolina's White Democratic Men (18 percent of the Democratic vote in 2008)
In 2008, white men in South Carolina didn't choose Clinton or Obama. According to exit polls, nearly half of them (45 percent) backed ex-North Carolina Sen. John Edwards. Clinton won white women, while black men and black women backed Obama.
Back then, Edwards was the only white male candidate but also the most populist of the three. Sanders, while a much different politician than Edwards, may have a similar appeal to white men in South Carolina.
4. South Carolina's Evangelicals (64 percent of the GOP vote in 2012)
Like in Iowa, the majority of the electorate in South Carolina is likely to be self-described evangelicals. But at least in the last two primaries there, the Christian conservatives in South Carolina voted differently than in Iowa.
In 2008, John McCain did terribly in Iowa, then won about 27 percent of the evangelical vote in South Carolina. In 2012, Santorum won the evangelical vote in Iowa but lost it in South Carolina to Gingrich, despite a controversy that emerged before the primary about the former House Speaker's marital infidelity.
More than 40 percent of the vote in South Carolina is expected to be in the state's northern area, known as the Upstate. This area is full of evangelicals who are also very conservative voters, which favors Cruz.
But some of these voters, while identifying themselves as evangelicals, are not as conservative. They could be very amenable to Trump, who is not as openly devout as candidates like Cruz and Rubio.
There is some evidence from national polls that Trump's strongest supporters are either former or current Democrats who feel distanced from the party and now largely back Republican candidates. A recent New York Times analysis illustrated this dynamic, showing Trump's support being very high in states like Mississippi, Louisiana and West Virginia that have drifted to the GOP in the last two decades.
Trump's campaign has intentionally had the mogul appear in towns like Mobile, Alabama, where they feel he has a natural support base. These towns often have sizable minority populations, but as the Washington Post recently reported, Trump's events in these areas are overwhelmingly attended by whites. In many of these towns, job losses and wage stagnation have created deep frustration with the state of the economy.
South Carolina is full of towns and cities with high black populations and also large numbers of working-class whites, much more so than Iowa and New Hampshire, which have little racial diversity.
If Trump is building a new coalition in the Republican Party of white working-class voters, South Carolina could be the first state to illustrate that phenomenon.
5. The Republican Insiders' Choice (28 percent of the GOP vote in 2012)
The "establishment" candidate, the one with lots of support among GOP elites, has traditionally won the Republican primary in South Carolina: George H.W. Bush (1988), Bob Dole (1996) George W. Bush (2000), McCain (2008). But 2012 broke this pattern, when Romney captured only 28 percent of the vote, compared to Gingrich's 40 percent.
Romney, a Mormon from Massachusetts, may have been a particularly poor fit for South Carolina. That said, he still won more than a quarter of the vote there.
This "establishment" bloc in particular could help Bush recover from his relatively weak showings in Iowa and New Hampshire. When longtime South Carolina U.S. Sen. Lindsey Graham quit his longshot campaign in December, many of his backers went to Bush, even as the ex-Florida governor was way down in polls. Eventually, Graham himself endorsed Bush.
What's not clear if this insiders' bloc still exists or has much power.
In 2010, Nikki Haley won an insurgent campaign to become South Carolina's governor, as did Tim Scott to become one of the state's U.S. House members and then a senator. Haley, as governor, backed Romney in 2012, only to watch him be defeated in the state by Gingrich.
And in this race, the insiders are divided. South Carolina Lt. Gov. Henry McMaster is for Trump, U.S. Rep. Trey Gowdy and Scott back Rubio, Graham is for Bush, U.S. Rep. Jeff Duncan is behind Cruz.
Bush allies said that George W. Bush is very popular here, and that will help his brother. They argue there is essentially a "Bush wing" in South Carolina of people who backed Jeb Bush's father and brother.
If that bloc does not get behind Jeb Bush on Feb. 20, his candidacy is likely doomed.