Regardless of how we feel about Kamala's confrontation with Joe last week, there are other factors contributing to Joe's decline in the polls.
First, let's take the entire exchange about busing out of the equation.
This is going to come across harsh and may anger some people, but we have to be honest with each other: Democrats tend to be very visual and that often leads to ageism. In my opinion, Biden has slipped in the polls because older candidates are held to a different standard when it comes to gaffes and mistakes. For a candidate in his/her mid-70s to make it through a democratic primary, s/he would have to be at least 3 times better than the other competitors. There can be zero doubt in democratic voters' minds about a candidate's physical and mental fitness. Republicans are OK with grey area candidates like reagan and trump. I guess because someone else is pulling all the strings so it doesn’t matter. But we're not OK with that.
So that is what people were tuning in to the debate to assess—if Joe is up for the task. Unfortunately, a lot of viewers who adore Joe were left with more questions than answers after watching his performance in the debate. Some voters had not seen Biden in years and were stunned by how his appearance had changed. It doesn’t help that most of us were watching on 1080P or 4K HD screens. Then when you add in some of his responses, for example, his response to the question about the first thing he'd do if elected president, it just wasn’t good. A younger candidate could get away with that but not a 76 year old.
Full disclosure: I support Elizabeth Warren for president, but I’ve spent the past several weeks frustrated by all the over the top and often unfair attacks on everything Biden says and does.
Now I feel like Biden’s detractors were, albeit inartfully, trying to get everyone to understand that he isn’t as electable as we all think. But that leaves the question…. Who is? Is it Kamala? I would love that but can she bring out the democratic vote AND get at least 39% of the white vote? I actually think Cory Booker would have a better chance because he wouldn’t have to deal with sexism, birther rumors, spouse scrutiny, or explaining actions taken as state prosecutor. Still, Cory isn't doing well in the polls, and frankly, his desperate attempts to get attention have not gone unnoticed.
On a side note, Rachel Maddow has openly expressed her disappointment about Governor Bullock not qualifying for the debates, despite 20+ other candidates being on the stage. I wonder if her disappointment is due to thinking Bullock is the only candidate capable of a decisive victory next fall?