In 2008, Hillary Clinton's road to the White House was jammed by a junior senator from Illinois who convinced black voters, many longtime Clinton supporters, to switch allegiance.

This time, an elderly white socialist from Vermont is trying to do the same. And Sen. Bernie Sanders is doing well enough that he's hoping to make South Carolina, with its sizable black minority, a competitive race.

Conventional wisdom has it that South Carolina, which holds its primary on Feb. 27, is Mrs. Clinton's to lose. After all, she's always done well with minorities, especially African Americans, who account for 28 percent of the population in the Palmetto State.

Clinton has a 64-27 percent lead over Sen. Sanders among likely voters in South Carolina's primary, a lead that jumps to 74-17 percent among likely black voters, according to an NBC News/Wall Street Journal/Marist poll released late last month. Other estimates had her garnering as much as 80 percent of South Carolina's black vote in the primary.

In fact, Clinton is counting on minority voters, especially African Americans, to serve as a sort of "firewall," stopping Sanders' progress in South Carolina and other southern states with early primaries, as outlined in a Clinton campaign memo earlier this week.

But Sanders appears to be chipping away at Clinton's "black voter firewall."

His supporters are canvassing southern states, circulating fliers touting Sanders' history and policies: he marched with Martin Luther King in 1963 and he supports criminal justice reform, a $15 minimum wage, and tuition-free colleges and universities, all of which would benefit African American communities.

Packaged correctly, his raison d'etre – his passionate mission to end income inequality – may resonate in lower-income black communities.

And while Clinton has the lion's share of endorsements from prominent black leaders, Sanders is picking up steam with endorsements from Princeton University professor Cornel West, The Atlantic magazine correspondent Ta-Nehisi Coates, and former NAACP President Ben Jealous, among others.

Those endorsements could pay off handsomely for Sanders, says David Ryden, a professor of political science at Hope College.

"Sanders' first order of business ought to be to get his ad-maker into the studio, and make a new shot highlighting the Ta-Nehisi Coates endorsement, and then blanket the state with it," says Professor Ryden. "Coates is the black public intellectual of the moment, and his endorsement is a big deal. It could start to turn the tide his way in South Carolina.”

And Sanders could take a page from then-Sen. Barack Obama's 2008 playbook and leverage his support among younger voters to persuade their parents and grandparents to vote for him. While older black voters still tend to support Clinton, some younger black voters are defecting to Sanders, according to a recent NPR report.

There is evidence that Clinton is feeling the heat.

A new poll of likely South Carolina Democratic voters has Clinton leading Sanders 47 percent to 28 percent. But more to the point, the poll shows Sanders cutting Clinton's lead there 17 percent in 30 days.

"This is a significant lead for Clinton but Sanders is closing fast," Phil Noble, President of the South Carolina New Democrats, said in a statement. "If Shakespeare is right and 'what's past is prologue,' then I'm not sure I'd sleep too well if I were Clinton."

Sanders met with prominent black leader Rev. Al Sharpton in Harlem Wednesday, sending a signal that he's serious about courting the black vote.

And in a recent article in The Nation, titled "Why Hillary Clinton Doesn't Deserve the Black Vote," Michelle Alexander makes the argument that policies Bill Clinton enacted and Hillary Clinton supported, like the crime bill and welfare reform, have devastated African Americans. The article sent waves through black communities – and chills down the spines of Clinton staffers.

Nonetheless, Clinton remains strong in black communities, and in South Carolina.

Among nonwhite voters, Sanders trails Clinton by nearly 40 percentage points nationally. What's more, Obama’s current job approval rating among blacks nationally is about 90 percent, and Clinton is running as an Obama surrogate.

In New Hampshire, where Sanders handily defeated Clinton, and Iowa, where Clinton won with a razor-thin margin, electorates were more than 90 percent white. By contrast, only 65 percent of voters were white in the 2008 Democratic caucus in Nevada, and only 43 percent were in South Carolina.

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As for Clinton's performance in South Carolina, a FiveThirtyEight weighted polling average predicts Clinton will win 60 percent of the vote to Sanders' 29 – a margin Sanders would be hard-pressed to overcome by primary time.

Sanders may not win enough black voter support to win the southern primaries, but he's not letting Clinton take black voters for granted.