Here's the issue for Joe Biden. His campaign strategy seems to be "I'm not Donald Trump." After four years of bringing out everything negative that could possibly be said about DJT there just isn't that much more ammo in the "AR-14" for Biden. The Reject Trump folks are already baked in the cake. President Trump has been innoculated. Joe Biden got to come up with a reason to make people vote FOR him and not AGAINST DJT if he has any hope winning in November. There is no uplifting message or positive change articulated so far that is widely accepted among anyone that is persuadable.
Meanwhile, the Trump campaign has not yet started its own ad blitzes or pointing out the way to add to Joe's negatives. Every time Joe opens his mouth he hurts himself; he's hurting his own cause. A nation at peace and prosperity is a hard thing to run against (and Wuhan corona virus isn't going to change that). He needs to be out there, showing good ideas, compassion for people, and persuading those that are not already baked in the cake. And he can't do it; it seems he is temperamentally and perhaps cognitively incapable of doing so. His numbers are going to go down when he starts getting hit with the negative ads that he is creating with his own actions and when people are reminded that their lives are pretty good right now.