Presidential re-election campaigns are normally a referendum on the performance of the incumbent. This one is no exception.
Normally, however, the challenger has to convince voters he (or someday she) would do as POTUS a better job than the incumbent. This year’s challenger doesn’t face that hurdle.
We have four years of data about a Trump presidency and he did a better job as POTUS. That makes this a tough sell for Biden and his handlers.