I don't have any idea about his general health, but to me it's obvious he's declining mentally. That's not a stab at Joe at all, it's life. I don't think it's going to harm his campaign unless he actually falls apart on camera.
Joe is the comfortable vote. All the republicans that are sick of having a rude asshole as president can vote for middle of the road Joe. All the democrats that thought Liz and Bernie were to far left can vote for Joe. Pretty much everyone on earth knows that Joe will bring some dignity back to the White House. All of that bodes well for his election, but I also think a lot of people doubt he'll make four years, but don't really care as long as he has a decent VP.
Just my opinion, I could be wrong.
More than dignity. It's also about honesty, good will, sincerity, integrity & common decency.