Former Vice President Joe Biden’s enduring support among black voters -- an entrenched bedrock of the Democratic Party -- remains high, with nearly half of black Democratic-leaning voters backing the elder statesman, more than twice his closest competitor, in a new Washington Post/Ipsos poll.

The only other Democrat to clinch double-digit support among black Democratic-leaning voters is Vermont Sen. Bernie Sanders, who secured 20%, and whose advocacy of racial justice dates back to the Civil Rights Movement when he was a student leader of the Congress of Racial Equality in Chicago and was arrested during protests on one occasion.

Rounding out the top three is Massachusetts Sen. Elizabeth Warren, who after seeing rising support among African Americans over the summer and early fall, following early struggles to win over the pivotal voting bloc in the first few months of the primary, now stands at 9% support.

Behind Warren is former New York City Mayor Mike Bloomberg, who only a week before announcing his eleventh hour bid for the White House in November, apologized for his longstanding and vehement support for "stop-and-frisk" policing -- a controversial policy that was ruled unconstitutional by a federal judge for being racially discriminatory.

Bloomberg is tied at 4% with New Jersey Sen. Cory Booker, who is African American, and has focused much of his campaign on helping highlight issues impacting disenfranchised minority communities and voters.

The poll, conducted by the Washington Post and Ipsos, sampled 769 Democratic-leaning registered voters, with a margin of error of +/- 4 points, from a national sample of 1,088 non-Hispanic black adults age 18 and over.

Biden’s commanding lead fortifies his strategy

Biden’s commanding double-digit lead atop his Democratic rivals in this poll - an edge he is banking on in his quest for the Democratic nomination - is a strong signal for the former Delaware senator nearly three weeks ahead of early voting, and a little over a month before South Carolina’s primary, where nearly 30% of the population is African American.

The ability to build a broad coalition, Biden’s advisers have contended throughout the primary, sets him apart from the rest of the Democratic field. A key part of that coalition, his team insists, are African Americans, since a Democrat has not secured the nomination without amassing substantial support from black voters since 1992, according to senior advisers to the campaign.

Biden, too, insists his grip on a broad coalition, particularly African Americans, is steady.

"I get broad support from the African American community, the black and brown community, with the working class, middle class folks," Biden told NBC News in an interview earlier this week. "And so I've always I've always had broad support within the party."

More than any other Democrat in the presidential contest, Biden has collected the most endorsements from members of the Congressional Black Caucus, with a total of nine, and has also garnered several other high-profile endorsements from African Americans, including Atlanta Mayor Keisha Lance Bottoms, Richland County Council Chair Bernice Scott and her "Reckoning Crew," a group of 100 predominately black female activists in South Carolina following California Sen. Kamala Harris’ departure from the race, and his senior adviser Symone Sanders, who previously worked on Sanders’ campaign in 2016.

In this poll, Biden’s foothold among black voters appears without its fissures -- he tops his Democratic opponents across a number of factors that have divided the field throughout the primary, including electability, handling issues important to the community, uniting the country, strongest personal character, and closely aligning with them on the issues.

Over half, 53%, of Democratic-leaning blacks say Biden has the best chance of beating President Donald Trump. Nearly one-third, 32%, say Biden would be the best candidate to handle issues that are important to black Americans, 43% say he would do the most to unite the country, one-third say he shows the strongest character and 35% say he lines up closest to voters on the issues.

Biden’s ability to solidify his support, political experts told ABC News, stems from a perception of electability.

"For most Democrats, they are looking for a candidate that can be President Trump and President Biden is perceived by most Democrats, and particularly African Americans, to be the candidate who could most beat Trump," said Fredrick Harris, a political science professor at Columbia University, with a focus on African American politics.

That assertion is backed by the poll, in which 57% of Democratic-leaning blacks said nominating a candidate who is most likely to defeat Trump is most important, compared to 33% who opted for nominating a candidate who aligns most closely to them on the issues.

Despite Biden’s record with shepherding the 1994 crime bill through Congress, which some critics say helped lead to mass incarceration among blacks, on busing and other issues involving desegregation and race in the 1970s - a core tenet in California Sen. Kamala Harris’ early attacks on the former vice president - and his handling of Anita Hill’s testimony during Supreme Court Justice Clarence Thomas’ confirmation hearing, black voters remain the backbone of his support - and for one key reason, according to Harris.

"Despite all that, Biden's being vice president under Barack Obama, who is still very popular among African Americans, make him a strong candidate among them, among African Americans," he said. "It's almost like apostolic succession in a sense - that you know that President Obama has symbolically sort of laid his hands on Biden, not necessarily endorsing him but had enough confidence to have him as his vice presidential candidate."

"In many ways, electing him would be an extension of the Obama legacy, I suspect, to many black voters," he added.

Of those black Democrats polled, 56% said they are more likely to vote for Biden since he served under President Obama for eight years. Forty-one percent said his tenure as vice president to the nation’s first African American president doesn’t make a difference, and only 2% said it would make them less likely to vote for him.

The race for the black vote

While the other contenders attempt to narrow Biden’s lead among this core constituency of the Democratic base, both "knowing" a candidate and their commitment to the black community are paramount in drawing their support, political experts say.

Beyond the former vice president, fault lines exist between black voters and the three other front-runners in the contest - Warren, Sanders and former South Bend, Ind. Mayor Pete Buttigieg.

For Warren, despite her litany of policy proposals that possibly buttressed her summer spike, she still faces an uphill climb with this key demographic.

"She's been the best in terms of providing a menu of policy proposals, and particularly policy proposals that are targeted to black communities," Harris said. "Her problem is that, which it is with a lot of candidates, is sort of where have you been before you ran for president?"

Harris says, Warren, like most of the candidates, should "demonstrate her commitment to issues that face African American voters" to improve her standing.

Unlike Warren, Sanders may be known, according to Harris, but he still falls short in showing his longstanding commitment to the community. Harris acknowledged Sanders’ activism during the Civil Rights era but he asked rhetorically, "so what's happened in the 70s, 80s and 90s."

He also critiqued Sanders for touting policy proposals that he believes are not "targeted."

"The idea that you have some sort of trickle down, sort of universal policies without any targeted policies, maybe off putting to some black voters," he said, adding that Warren is more "apt" to talk about targeted policies.

The former Burlington mayor might still be plagued by a debate, emanating from his 2016 presidential bid, about whether he talks about inequality in an "intersectional kind of way," meaning not only touching on divides across class but across race, as well, said Andra Gillespie, an associate professor of political science at Emory University.

"While Sanders has improved sort of his rhetoric about the balance of race and class," she said, "there's still some room for improvement. And there's so many people who sort of developed and crystallized their positions of him or their impressions of him in 2016."

But political experts also pointed to Warren’s, Sanders' and Buttigieg's capacities to confront questions around electability - one factor that has continued to shape the contours of the race, particularly for black voters.

"I think that there could be questions for all three of [those] candidates...about whether or not they can actually beat Donald Trump in the general election," Gillespie said, adding that voters might "strategically" make the decision to not take a chance on supporting a candidate who might not win the nomination or beat Trump.

But no contender in the top tier more than Buttigieg has such a stark deficit with black voters. In the poll, only 2% of black Democratic-leaning voters are backing the former U.S. Navy Intelligence officer.

Buttigieg has consistently struggled to make inroads with this voting demographic from the onset of his bid, even conceding in May in North Charleston, South Carolina that he was having trouble reaching black voters, before asking for help.

On Thursday, Buttigieg netted an endorsement from Maryland Congressman Anthony Brown, the first black member of Congress to back his campaign.

Harris said Buttigieg’s early stumbles, mainly the fallout from a white police officer shooting and killing a black man, Eric Logan, in his city in June - which exposed an estranged relationship between the city’s black community and its police department - is in part an underlying thread in his inability to win over black voters. But political experts also note it is the once-little-known mayor’s unknownness.

"Black voters don't know who he is," Harris said before posing, "Where has been his commitment to these issues prior to running for president? I mean, what we see as a murky history on those issues as mayor of a midsize city in Indiana. A city that has a large, sizable black population but a state that does not...His record is either unclear or, or pretty much non-existent."

Buttigieg’s lackluster support could also possibly derive from a variety of sources, Gillespie said.

"I don't want to be naive and think that there aren't people who, you know, wouldn't support Mayor Pete because of his sexual orientation," she said. "I'm sure that that is part of it...but that's not the only challenge that he faces...He hasn't won a statewide contest. He hasn't represented an area that is as large as a congressional district, so there are lots of reasons for people to sort of find his candidacy premature and also think that he might not be the one to be able to go to the distance against Donald Trump."

In fact, the numbers show that the majority of black Democrats in the poll - a net 62% - say they would be either enthusiastic or comfortable voting for a gay man as president, while a combined 36% expressed reservations or that they were uncomfortable.

A national Quinnipiac University poll from April 2019 which found that 66% of black U.S. voters are open to a gay man as president and 24% said they were not open.

In that same poll, 70% of U.S. voters said they were open to electing a gay man as president while 23% said they were not open.

Buttigieg isn’t the only candidate grappling with low name recognition and little connection to the black community.

In another question touching on aversion to candidates in the field, Hawaii Congresswoman Tulsi Gabbard sits atop the field as the candidate who black Democratic-leaning voters definitely won’t consider supporting, with 23%. In a close second is Bloomberg, with 17%, followed by Buttigieg with 15%.

Black voters are 'crucial' in Democratic politics

Black voters have an outsized role in the Democratic primary, with the pivotal influence that comes with representing 21% of the Democratic electorate, according to data from the most recent presidential election.

In 2008, black voters, a key component of then-candidate Obama’s broad base, vaulted him to a win in South Carolina, and ultimately, the nomination. No modern candidate for president has won the party’s nomination without securing a majority of the black vote.

"Black Democrats are the most loyal constituency within the Democratic Party," Harris said. "They are a constituency that a super majority of their votes collectively go to the Democratic Party - somewhere between 90 and 98% or more - during presidential elections...Their votes are absolutely crucial in determining the outcome of the Democratic Party nominee for the presidency."

Since the primary electorate is "truncated," Gillespie said, and a sizable portion of African Americans historically vote Democratic, "they're going to have a tremendous amount of influence in the party."

She also posited that the focus of certain policy discussions and efforts by the candidates, particularly those in the top tier, to court the African American vote this cycle reflects the significant role black voters play in the primary.

"What we've seen is kind of a recognition of, one, the importance of African American voters, which I think people have long realized," Gillespie said. "I think that there's also been a recognition that I think has been pushed forward by activists...that candidates have to address these issues if they expect to be taken seriously by African American voters."

Looking ahead to the general election, the poll shows that a combined 81% of black Americans are either certain or are likely to vote in November and a net 83% said the outcome of the election mattered a great deal to them.

Some 89% of respondents said it was personally important to them that President Trump not win a second term as president.

Regardless of who wins the nomination, black voters are clearly siding with the Democratic Party over President Trump, despite an effort by his campaign to coalesce what is usually a dedicated Democratic-leaning voting bloc around his re-election.

Trump trails all the Democrats included in a hypothetical head-to-head matchup question in the poll, with at most, 5% saying they would back the incumbent Republican over a Democrat.

ABC News’ Molly Nagle, Justin Gomez, Beatrice Peterson and Devin Dwyer contributed reporting.