Democratic presidential candidate Hillary Clinton gestures to supporters at her New Hampshire presidential primary campaign rally on Feb. 9 in Hooksett, N.H. (Elise Amendola/AP)

With New Hampshire in the rearview mirror, Hillary Clinton is looking ahead to South Carolina, Nevada and other states where support from African American voters will be crucial if she wants to clinch the Democratic nomination.

Then came this: Influential Atlantic writer Ta-Nehisi Coates, who has publicly criticized Bernie Sanders for his opposition to monetary reparations, will be voting for the Vermont senator, he told Democracy Now's Amy Goodman on Wednesday.

"I'm stunned, but I'm pleasantly stunned," Coates said of Sanders's New Hampshire victory.

Coates may have pushed back against calling it an endorsement, and he still remains critical of Sanders regarding reparations (. But where Coates landed this primary season underscores a potential vulnerability for Clinton: her weakness among young voters could chip away at the support she has among black and Latino voters — and be a boon for Sanders, whose base of support skews young.

When asked about monetary reparations for slavery, Sanders and Clinton have both said they favor investments for minority and marginalized communities. Coates on Wednesday said that despite those similar positions, "I expected more" of Sanders.

Coates also told Goodman: "Like a lot of people, I’m very, very concerned about Senator Clinton’s record. I’m very, very concerned about where her positions were in the 1990s, when we had some of the most disgusting legislation in terms of our criminal justice, really, in this country’s history."

Coates isn't alone. Former NAACP president Benjamin Jealous has forcefully endorsed Sanders. "I looked at his record," Jealous, the youngest person to head the civil rights organization, said Tuesday. "On the issues that Dr. Martin Luther King referred to as the 'giant triplets of evil' — racism, militarism and greed — Bernie is the clearest and the most consistent."

That critique was echoed by "New Jim Crow" author Michelle Alexander, whose book helped invigorate the public dialogue about racism and mass incarceration. "Black voters have been remarkably loyal to the Clintons for more than 25 years," Alexander wrote Wednesday, adding that Bill Clinton "presided over the largest increase in federal and state prison inmates of any president in American history.”

Noting that Hillary and Bill Clinton have since said they regret the crime bill and the policies of tough-on-crime era, Alexander continues: "But what about a larger agenda that would not just reverse some of the policies adopted during the Clinton era, but would rebuild the communities decimated by them? If you listen closely here, you’ll notice that Hillary Clinton is still singing the same old tune in a slightly different key."

Sen. Bernie Sanders raises a fist as he arrives for a breakfast meeting with Al Sharpton at Sylvia's Restaurant on Wednesday in Harlem, N.Y. (Seth Wenig/AP)

Sanders also has campaign surrogates such as  rapper Killer Mike, who has publicly argued with Coates about the Vermont senator's position on reparations.

But whether such public proclamations are outliers or signals of something deeper remains to be seen. Clinton's support among African American voters around the country is deep. In South Carolina, nearly three-fourths of likely black primary voters are backing her, according to a NBC News/Wall Street Journal/Marist poll conducted in January. (Samples sizes for the survey, conducted before New Hampshire and Martin O'Malley's exit from the race, include 100 people or more.)

That same poll found 81 percent of African Americans in the state who are 45 and older support her, compared to 11 percent who supported Sanders. A majority of likely black South Carolina voters under 45 also said they're voting Clinton.

And Clinton has her surrogates as well, including black leaders who are now vocally criticizing Sanders on issues of race.

"Bernie Sanders as mayor, as a member of the House, as a member of the United States Senate, has been missing in action on issues that are important to the African Americans," said Rep. Hakeem Jeffries, a Democrat from New York, The Post reported. "There’s no credibility to the things that are being said at the twilight of his political career."

Looking ahead to Nevada and elsewhere, Clinton and Sanders have both signaled the importance of shoring up support among non-white voters. Clinton left New Hampshire before Tuesday's primary to visit Flint, Mich., a predominately black city with a water supply poisoned by lead. And the day after her New Hampshire loss, news emerged that Clinton's allies formed a $25 million effort to mobilize African American and Latino voters

Sanders had a very public breakfast with Al Sharpton at Sylvia's restaurant in Harlem on Wednesday (Sharpton said he's waiting until after he meets with Clinton to make an endorsement).

“But our issues cannot be marginalized,” Sharpton said later, The Post reported. “In January of next year, for the first time in American history, an African American family will be moving out of the White House. I do not want black concerns to be moved out with them.”

[This post has been updated.]