ROCK HILL, S.C. — Joe Biden’s front-running presidential bid will live or die by the black vote. His campaign finally acknowledged it this week.

Advisers to the former vice president began lowering expectations about winning both Iowa and New Hampshire — where more than 90 percent of the primary vote will be cast by white voters — and directing attention toward South Carolina and the South, where black voters will cast a majority of the primary vote in a handful of states on Super Tuesday.

It doesn’t mean Biden is conceding the first two nominating contests, just that his campaign views South Carolina — where more than 60 percent of the primary voters are African American — as the one early primary it absolutely cannot afford to lose.

It’s the clearest evidence yet of his campaign’s theory of the case, which is rooted in Biden’s strength among black voters — a vestige of the former vice president’s service in the Obama administration. African Americans back Biden by outsized margins in both the Palmetto State and nationally, which makes South Carolina the linchpin of Biden’s early-state strategy.

South Carolina, the campaign expects, will function as a firewall within the early state gauntlet and as a springboard to Super Tuesday, where anywhere from two-thirds to 28 percent of the electorate is black, depending on the state.

“South Carolina is key because it’s the first state with a substantial African American population. And black voters have traditionally been the key to securing the Democratic nomination and, right now, they’re with Joe Biden,” said Symone Sanders, a top Biden adviser. “If one wants to say it’s a must-win, we think we’re going to do extremely well there.”

According to two advisers who requested anonymity and a source who spoke with Biden, Biden’s campaign believes he needs to win two of the first four early states. One of those states probably needs to be Iowa or New Hampshire, the sources said. But he can’t get blown out in either — or in the third early state, Nevada, which Biden has visited less often than the others.

“I don’t see any path for Biden to win the nomination without South Carolina,” said Mark Longabaugh, a longtime Democratic strategist who’s neutral in the race and worked for Bernie Sanders' 2016 presidential campaign. “African American support for Biden is crucial for his candidacy.”

Winning black voters in South Carolina, the campaign hopes, would have a force-multiplier effect since any candidate who carries the black vote by big margins — in the southern states generally and in their heavily African American congressional districts specifically — gets a windfall due to delegate allocation rules.

“It’s a delegate game,” Sanders said, repeatedly mentioning that any Democratic nominee must build a “broad, diverse coalition” that primarily includes blacks, whites and Hispanics.

That point — a dig at the other candidates who have comparatively little nonwhite support — was emphasized repeatedly earlier this week during a “fall preview” conference call that the Biden campaign hosted with reporters.

During that call — for the first time — campaign officials began setting expectations for Biden’s early state performance.

“Do I think we have to win Iowa? No,” one senior adviser said, adding that the first caucus state is nevertheless “critical.” Later, turning to the first primary state of New Hampshire, the adviser noted that “as you all know, historically, there’s an incredible home field advantage for a Massachusetts candidate or a New Englander” — a not-so-subtle reference to Sens. Elizabeth Warren and Bernie Sanders.

Cliff Albright, co-founder of the group Black Voters Matter, and others who specialize in turning out the African American vote say black voters have stuck by Biden for two major reasons. First, he was the loyal running mate and No. 2 to the first African American president, Barack Obama. Secondly, he’s perceived as the most likely candidate to beat Trump.

Still, Biden’s strategy for the South could come apart depending on what happens up North. If he loses Iowa and New Hampshire, Biden could see his South Carolina advantage evaporate because he could no longer make a compelling electability argument after getting beaten in two major contests. That happened to Hillary Clinton in 2008 when Obama scored an upset win in Iowa and shattered her aura of invincibility.

“It spells trouble if he has slippage in Iowa and New Hampshire,” said Adrianne Shropshire, founder of the African American political group BlackPAC. She noted that South Carolina could be a must-win for all the candidates, not just Biden. “It’s important to him and it’s equally important to the other front-runners as well,” she said.

Biden’s advisers say they’re well aware of recent primary history — especially in light of the candidacies of California Sen. Kamala Harris and New Jersey Sen. Cory Booker, both of whom are black. But neither has, at this point in the 2020 race, come anywhere close to drawing the same level of support as Obama did in 2008.

As a result, a Biden win in South Carolina wouldn’t just give him momentum heading into the rest of the South, but it would also seriously damage the candidacies of Harris and Booker, said the Rev. Joe Darby, first vice president of the NAACP’s Charleston Branch and an influential pastor from Nichols Chapel AME church.

“If their numbers do not rise in South Carolina,“ he said, “it’s time for some serious prayer and thoughtfulness about what they do next it.”

“You can’t make the mistake Hillary made and take the black vote for granted. You’ve still got to work at it. And I think his [Biden’s] folks are working at,” Darby said. “He’s making the rounds.”

Biden, whose campaign co-chair is a former head of the Congressional Black Caucus, Rep. Cedric Richmond of Louisiana, began ramping up his black voter outreach in July, after Harris and Booker attacked his record on race.

Late last month, the campaign began stumping in select hair salons and barbershops to spread the word. Last week, he traveled to South Carolina for four rallies, including an event at historically black Clinton College in Rock Hill.

Before Biden traveled to South Carolina last week, he made a point to sit down with black reporters and gave an unprecedented ask-me-anything interview for 90 minutes, followed by another meeting with local African-American reporters.

Biden’s campaign has also hired a South Carolina faith director, Michael McLain, to network with churches, which provide a better way to reach African American voters in the state than going through the traditional party structure. More than 39 pastors in the state have endorsed Biden.

Biden’s wife, Jill Biden, privately attended a cookout with a black business fraternity this summer at the home of an influential African American senator, Marlon Kimpson, who represents a heavily black North Charleston district where the campaign set up a field office. And later this month, the campaign is dispatching Keisha Lance Bottoms — mayor of majority black Atlanta — to South Carolina.

On Sunday, Biden travels to Montgomery, Alabama, for his first visit as a 2020 candidate.

The key to maximizing delegates in Super Tuesday states like Alabama is to win big both statewide and in Democratic congressional districts.

“I would argue that it isn't necessarily district-specific as it is performance both statewide and across the districts,” political scientist Josh Putnam, who maintains the Frontloading HQ blog that tracks primary states and delegate counts, said via email. “Both Obama (2008) and Clinton (2016) cleaned up in that manner, sweeping through the African American-heavy South and building a delegate lead that ended up being small (Obama) to large enough (Clinton) but insurmountable. Biden is certainly seeking to replicate that, but it goes through South Carolina first (and that likely hinges on how the first three contests go).”

Biden’s adviser, Symone Sanders, said the campaign is ready to withstand multiple candidates fighting hard in the first three states. But the field will winnow by the time South Carolina rolls around on Feb. 29, followed by Super Tuesday three days later.

“We believe there are a number of people who are going to be competitive in Iowa and New Hampshire,” she said. “But not as many folks will be able to compete at the level we’re competing at when it comes to South Carolina and definitely when you go into Super Tuesday.”