WASHINGTON (CNN) Joe Biden leads the Democratic presidential primary but a tight race for second place has formed behind him as Sen. Elizabeth Warren leads Sen. Bernie Sanders by one point, according to a new CNN poll conducted by SSRS.

The former vice president is at 24%, Warren at 18% and Sanders at 17% are once again the only candidates to reach double-digit support. Three other candidates have 5% or support or more in the poll: Sen. Kamala Harris (8%), South Bend, Indiana, Mayor Pete Buttigieg (6%) and former Rep. Beto O'Rourke (5%). The remaining candidates all score 2% or less in the poll.

Biden's lead rests on his support among black voters, among whom he leads by a wide margin with 42% backing him and his nearest competitor -- Sanders -- earning just 12% support. Warren (23%) and Biden (21%) are about even among white potential Democratic voters, with Sanders not far behind at 15%. Among Hispanics who are Democrats or Democratic-leaning independents, Sanders stands at 24%, with four other candidates in double-digits: Biden at 18%, O'Rourke at 14%, and Warren and Harris each at 10%.

Biden's backing among black voters comes primarily among those over age 50 (53% in that group support him vs. 30% among those under age 50) and from those who are moderate or conservative (47% in that group support him). That mirrors the pattern among Democrats more generally, but holds to a greater degree among black voters. Sanders' strong showing among Latinos comes more from younger Hispanic voters than from older ones.

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