Issue No.1 for Biden: (other than his failed polices)
Biden is in cognitive decline and unwilling to debate Trump.
This is seen as a sign that his dementia is real and he is unfit to be President.
Biden has some cover regarding debates whether it is legitimate or not:
Neither Biden nor Trump debated during the respective primaries.
Biden and the MSM will falsely claim that Biden should not lower himself by debating a liar and an insurrectionist.