The poll, conducted from August 9-12 among 900 registered voters, put Biden ahead of Trump with 50 percent of the vote to the president's 41 percent.
In July, the former vice president's advantage over Trump widened to 11 percentage points from 7 points in the previous month.
Less than three months ahead of the presidential election, Biden holds a double-digit lead over Trump on the coronavirus response, health care, immigration, race issues, and uniting the country.
The incumbent president has an advantage over his challenger on the economy, regarded as the main issue by the majority of those surveyed, as well as on fighting crime.
