Support for Democratic presidential candidate Bernie Sanders among African American voters has increased, reaching similar levels to that of fellow candidate Joe Biden.

A new poll from NBC News and The Wall Street Journal finds that 20% of black voters are "enthusiastic" about the Vermont senator, compared to 16% who say the same about the former vice president. Forty-five percent say they are "comfortable" with Sanders, compared to 53% who are comfortable with Biden.

While 89% of registered black voters say they would vote for Biden over President Donald Trump in the 2020 election, 87% say they would cast their ballot for Sanders over Trump.

Sanders' surging approval among African American voters could be a troubling sign for Biden, who has bet that his support among black voters would boost his performance in upcoming Democratic primary battles in states with more racial diversity than Iowa and New Hampshire, where he struggled. South Carolina, where black voters make up about 60% of the Democratic electorate, holds its primary on Feb. 29.

The poll finds that aside from Biden and Sanders, Democratic presidential candidates have failed to gain much traction with black voters.

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Sen. Elizabeth Warren of Massachusetts and Former New York City Mayor Michael Bloomberg poll similarly among African Americans. Eleven percent say they are enthusiastic about Bloomberg, with Warren close behind at 10%. Thirty-two percent are comfortable with Bloomberg, compared to 36% who say the same about the senator.

Also neck-and-neck are Sen. Amy Klobuchar of Minnesota and Pete Buttigieg, former mayor of South Bend, Indiana. Twenty-five percent of black voters are either comfortable or enthusiastic about the senator, compared to 28% who feel the same about Buttigieg.

Among African American voters surveyed, 27% say they "have some reservations" about Bloomberg, followed by 24% who have reservations about Warren and Buttigieg. Seventeen percent of black voters say they are very uncomfortable with Buttigieg, followed by Bloomberg at 15%.

No matter where the Democratic candidates fall, all garner more support than President Donald Trump. Just 3% of black voters are enthusiastic about the president, with 4% saying they are comfortable with him. Fourteen percent have reservations, while 78% are very uncomfortable.

"The NBC News/WSJ poll used an oversample of black voters to gain greater insight into their views of the 2020 field," according to NBC . "Because the margin of error for black Democratic primary voters alone – a sample size of 139 respondents – stands at a high 8.31 percent, it is difficult to differentiate the true levels of support for each of the candidates."