While the world focuses this week on New Hampshire — where Vermont Senator Bernie Sanders has a solid, perhaps insurmountable lead — Clinton is racing to shore up African-American support in her “firewall,” a string of racially diverse states in the Deep South that she is counting on to stop the Sanders surge.

And the campaign’s first TV spot in the state, which began airing Thursday? It features Eric Holder, the country’s first black attorney general, testifying to Hillary Clinton’s record on civil rights.

WASHINGTON — At a historically black college in South Carolina last week, Bill Clinton gushed about his wife’s resume as a “change-maker.’’ Chelsea Clinton was slated to be close on his heels, speaking Saturday to women at an African-American church.


A recent Wall Street Journal/NBC News/Marist poll shows Clinton leading in the first of these states — South Carolina, which votes Feb. 27 — by a 37-point margin. That lead relies heavily on the support of black voters, who prefer Clinton over Sanders by 74 to 17.

Whether Sanders can maintain momentum in the primaries after New Hampshire will depend on how much black support he can pry away from Clinton. If he can’t demonstrate that he can build a more diverse coalition, his liberal movement probably will fizzle.

So the 74-year-old senator from one of the whitest states in the country is trying to broaden his appeal.

With tens of millions in small donations pouring in over the Internet, Sanders is spending heavily to build a campaign organization in South Carolina. He is airing ads on black radio stations about his record of fighting racism, from his college years to his career in the Senate, and in favor of criminal justice reform.

His campaign is paying more than 100 black organizers $15 an hour — the national minimum wage he is advocating for — to go door to door. Half of his South Carolina team had previously worked on Barack Obama’s 2008 and 2012 campaigns.


“What Sanders is doing here has forced the Clinton campaign to step up their game and understand that they cannot take the voters of this state for granted,” said Gilda Cobb-Hunter, a longtime state legislator who is African-American and who is choosing to remain neutral in the race. “I don’t foresee Sanders winning South Carolina, but I do expect he will get double digit support in the black community, and that in and of itself may be a victory.”

Sanders, a democratic socialist, nearly upset Clinton in Iowa, and he has a strong lead in polls in New Hampshire. But those states are two of the least diverse in the country — very similar, in fact, to Vermont.

The Clintons, who got their political start in Arkansas, have long relied on black voters for support.

To help highlight her commitment to minorities and send a signal to her supporters in states like South Carolina, Hillary Clinton planned to touch down in Flint, Mich., on Sunday — two days before voting starts in New Hampshire — to draw attention to the plight of families poisoned by lead in their water. Flint’s population is more than 50 percent African-American.

“It’s important for Secretary Clinton to win South Carolina decisively to demonstrate her strength within communities of color,” said Jaime Harrison, the first African-American to chair the South Carolina Democratic Party and who remains unaligned with either candidate.


Polls help explain her underlying strengths. Likely Democratic voters are tilted toward church-going black women older than 45. More than half consider their political ideology as moderate to conservative; only 10 percent consider themselves to be “very liberal.”

The campaign recently announced that a slew of high-profile African-American women, from politicians to actresses, would blanket the state in coming weeks to mobilize their networks in support of Hillary Clinton.

Obama beat Clinton by nearly 30 points in South Carolina 2008. But Sanders is no Obama.

The Sanders campaign, when discussing the Clinton firewall, prefers to describe it as including not just states with large black populations, but also Nevada, which has a Democratic caucus Feb. 20, a week before South Carolina’s. Nevada has a large Latino population and lots of unionized casino and hospitality workers.

Clinton’s campaign launched its first Spanish-language radio spot in Nevada on Friday, and Bill Clinton was dispatched there Friday and Saturday to pump up enthusiasm.

Tad Devine, one of Sanders’ top strategists, said internal campaign polls in Nevada, which he declined to share with the Globe, show that Sanders is beating Clinton among Hispanics under 50 years old.

“We can really test the firewall starting in Nevada,” Devine said. “South Carolina is the same thing.”

After the South Carolina primary comes March 1, the “Super Tuesday’’ of 2016, with 11 states across the country holding primaries.

Devine said the Sanders campaign might start expanding and adding resources in Virginia, Oklahoma, Tennessee, and even Arkansas.


He also feels good about Minnesota, where Sanders recently held a rally that attracted thousands; Colorado; and, of course, Vermont. He believes the campaign can make inroads as well in Massachusetts, where Clinton beat Obama last time.

“What we’ve begun to see in the wake of Iowa is there’s a lot of movement,” Devine said.

In South Carolina, Sanders drew the endorsement last week of a high-profile state legislator who represents the Columbia metropolitan area, one of five black state lawmakers so far who are supporting Sanders. (Clinton has endorsements from 16 black state legislators.)

Justin Bamberg, one of the five, made headlines recently when he flipped his endorsement from Clinton to Sanders. The head of the state’s Young Democrats, an African-American woman, also scooted from Clinton to Sanders.

“He’s passionate about making racial issues, economical issues, and social issues in our communities change for the better,” said Bamberg, 28, an attorney who is representing the family of Walter Scott, the unarmed black man shot in the back by a white police officer last spring.

Still, there are skeptics about Sanders’ ability to make a dent in Clinton’s support.

“A delicate but necessary question is how Senator Sanders manages to identify with the black community,” said Rev. Joseph Darby, the presiding elder of the Beaufort district of the African Methodist Episcopal Church, who has not endorsed a candidate. “I appreciate his message of a rising tide floating all boats, but I don’t get the feeling that he gets that there will still be some racial prejudice that affects how things play.”


Sanders responded clumsily last summer when protesters associated with Black Lives Matter interrupted one of his speeches and he threatened to leave the stage. He has since made amends, meeting with activists and speaking more forcefully about racial inequality.

Some critics, however, balk at his endorsement of Bill Press’s new book, “Buyer’s Remorse: How Obama Let Progressives Down,” whose cover features a quote by Sanders. They see it as a repudiation of the country’s first black president.

“That’s not going to help in South Carolina or the South,’’ said Bakari Sellers, a former state representative who cochaired Clinton’s millennial group. “This primary is about protecting and voting on the legacy of Barack Obama.”

During Thursday’s debate, Sanders made the effort to align himself with Obama after drawing criticism from Clinton. “Do I think President Obama is a progressive?” he said. “Yeah. I do.”

Sanders’ campaign and black supporters cite his long history of fighting for racial justice, marching with Dr. Martin Luther King Jr. and being arrested for protesting institutional segregation as a leader of the Congress of Racial Equality when he was a student at the University of Chicago.

On Wednesday, Bill Clinton sought to counter Sanders’ claim that his wife was not progressive enough. Addressing a crowd of more than 800 at Allen University, a historically black college in Columbia, the former president spoke about his wife’s first job out of law school, working for civil rights activist Marian Wright Edelman at the Children’s Defense Fund in South Carolina.

He recalled Clinton and Edelman working to stop African-American teenagers from being thrown into adult prisons.

“She was sent to South Carolina to do something more relevant to the present day, when there are too many people in prison, especially people of color, who did not do anything worth these prison sentences,” Bill Clinton said. “She hadn’t been elected to anything, but she sure did make good things happen.”

Tracy Jan can be reached at tracy.jan@globe.com. Follow her on Twitter @TracyJan. Annie Linskey can be reached at annie.linskey@globe.com. Follow her on Twitter @AnnieLinskey.