Mr Biden is up six points in each state, 48 per cent to 42 per cent in Wisconsin and 49 per cent to 43 per cent in Pennsylvania, the poll showed.
By a wide margin, voters surveyed said things in America are going “badly”, and Mr Trump’s handling of the coronavirus pandemic was a major issue. About two thirds of voters reported disliking how Mr Trump “handles himself personally”.
Days before Mr Biden is expected to announce his choice of running mate, a majority of voters suggested the pick was “not at all” or “not very” important to them.
The surveys were conducted Aug 4-7 for CBS by YouGov and were based on representative samples of 1,009 registered voters in Wisconsin and 1,225 in Pennsylvania. The margins of error were plus or minus 3.7 percentage points in each poll.
The RealClearPolitics average of polls for Wisconsin, including the latest CBS reading, shows Mr Biden up 5.2 points. In Pennsylvania, Mr Biden is up by 5 points, according to the RealClearPolitics average.