As the Feb. 27 South Carolina Democratic primary approaches, Hillary Clinton and Bernie Sanders are racing to capture endorsements from prominent leaders in the black community. After all, 28 percent of the population in the Palmetto State is African American and capturing their support is crucial to winning the state.

But do endorsements by black leaders necessarily translate into votes?

Mrs. Clinton is counting on black voters to serve as a sort of "firewall," and polls show black voter support for her is high, but a number of black leaders, including Spike Lee, are endorsing Senator Sanders, who is trying to cut into Clinton's lead with black voters.

The director and black activist endorsed Sanders in an ad telling South Carolina voters to "Wake up!"

"This is your dude, Spike Lee. And you know that I know that you know that the system is rigged! For too long we've given our votes to corporate puppets. Sold the okie doke. Ninety-nine percent of Americans were hurt by the Great Recession of 2008, and many are still recovering," Lee said in the ad released Tuesday. "That's why I am officially endorsing my brother, Bernie Sanders."

He's not the first prominent black figure to back Sanders. While Clinton has the lion's share of endorsements from prominent black leaders, including the support of the campaign arm of the Congressional Black Caucus, Sanders is picking up steam with endorsements from Princeton University Prof. Cornel West; writer and The Atlantic correspondent Ta-Nehisi Coates; former NAACP President Ben Jealous; performer and civil rights activist Harry Belafonte; and Erica Garner, the daughter of Eric Garner, the Staten Island man who died after police put him in a chokehold.

"This battle over endorsements of key black figures is really interesting. I think there's something of a hierarchy of black leadership that may impact the effectiveness of endorsements by different figures," says David Ryden, a professor of political science at Hope College in Michigan. "The black vote in South Carolina is a heavily religious and evangelical one. That in tandem with the politicized nature of the black church gives black pastors and religious leaders a special influence on how their flock might vote.... Black voters also value the ability of their local political leadership to respond to their interests, both rhetorically and in more tangible ways."On both of those fronts, Professor Ryden says, Clinton appears to have a substantial edge over Sanders.

A recent CNN/ORC South Carolina poll showed Clinton with 65 to 28 percent lead over Sanders among likely voters. Other polls show that lead jumps to 74 to 17 percent among likely black voters. Some estimates have her garnering as much as 80 percent of South Carolina's black vote in the primary.

In fact, Sanders is trying to turn the tide with endorsements from black leaders, but political scientists differ on the importance of endorsements in political races.

"Data doesn't suggest that endorsements move too many votes," Pearson Cross, a political scientist at the University of Louisiana at Lafayette, told the local Louisiana News Star. "Still, candidates love to be endorsed by people who support their principles."

That's because "an endorsement is not going to change someone's mind" if the voter was inclined to vote for one candidate over another, Joshua Stockley, a political scientist at the University of Louisiana in Monroe, said. "They only serve to legitimize how people are already leaning."

Endorsements don't necessarily translate directly into votes, but they can. High-profile endorsements are actually primarily a tool to attract donors, volunteers, and positive media attention that campaigns hope trickle down into votes, particularly from last-minute, undecided voters in a close election.

"I think the endorsements of folks like Cornel West and Ta-Nehisi Coates – that is academics and public intellectuals – probably operate at a lesser level. So while not insignificant, they probably have less pull with black voters," says Professor Ryden. "For celebrity endorsements like that of Spike Lee, I'm just not sure. It would depend on the ability of the public figure to penetrate the consciousness of the average voter. Not sure if Spike Lee is that kind of public figure or not."

In fact, it's the the endorsements of party elites, not celebrities or public figures, that appear to have the most impact on a candidate's chances of securing the nomination. "Since 1980, the single best predictor of a party’s nominee is the number of endorsements from party elites — elected officials and prominent past party leaders — in the months before primaries begin," The New York Times reported last year.

Nonetheless, that hasn't stopped either of the candidates from courting prominent figures in the black community.

"Bernie takes no money from corporations. Nada. Which means he's not on the tape, and when Bernie gets into the White House, he will do the right thing," Lee said in Sanders's new South Carolina ad. "Enough talk. Time for action."

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It's not clear how much Lee's endorsement will help Sanders, but a new poll of likely South Carolina Democratic voters shows Sanders cutting Clinton's lead in the Palmetto State 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."