The SurveyUSA poll, which was released on Monday, found that Biden enjoyed the support of 32 per cent of likely Democratic primary voters nationwide, while Massachusetts Senator Elizabeth Warren garnered 22 per cent backing as runner-up, reports Xinhua news agency.
Vermont Senator Bernie Sanders was place on the third position in the poll, trailing Warren by 5 percentage points.
California Senator Kamala Harris, who is of Indian and Jamaican descent, fell behind Sanders by 10 points, signalling a wide gap between the three top-tier contenders and the rest in the field.
South Bend, Indiana, Mayor Pete Buttigieg followed Harris with a 5 per cent support.
Support for the other Democrats stood at 2 per cent or less.
Twenty-one per cent of the respondents said that their second choice would be Warren if their top candidate were to drop out.
Nineteen per cent said the same of Sanders, followed by 17 per cent who said the same of Biden.
The poll interviewed 1,071 likely Democratic primary voters nationwide on October 15-16, after the fourth Democratic debate in Ohio.
The poll has a credibility interval of 3.7 percentage points.
According to another poll released on Monday, Biden, Warren and Buttigieg were the top three candidates in the early caucus state of Iowa.
( With inputs from IANS )