A SurveyUSA poll found Biden enjoys the support of 32 percent of likely Democratic primary voters nationwide, while Senator Elizabeth Warren of Massachusetts garners 22 percent of the support as runner-up.
Senator Bernie Sanders of Vermont was the third in the poll, trailing Warren by 5 percentage points.
Senator Kamala Harris of California fell behind Sanders by 10 points, signaling a wide gap between the three top-tier contenders and the rest of the field, Xinhua news agency reported.
Mayor Pete Buttigieg of South Bend, Indiana followed Harris with a 5-percent support.
Support for the other Democrats stood at 2 percent or less.
Twenty-one percent of respondents said that their second choice would be Warren if their top candidate were to drop out. Nineteen percent said the same of Sanders, followed by 17 percent who said the same of Biden.
The poll interviewed 1,071 likely Democratic primary voters nationwide on Oct. 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.