In the primaries he was national leader for a long time, then slipped, then his numbers snapped back to form on Super Tuesday.
Biden has consistently led Trump in national polling by +7 on average. (Harry Enten spoke about this the other day).
Biden is boring and gaffe prone but is viewed as genuine and empathetic - and experienced. I think this is what insulates him from attacks. People know/like 'Uncle Joe' even though he's not exciting.
He did much better with white working class voters (including in the Midwest/blue wall states) this time than Hillary did, who struggled against Bernie in this regard.
Biden's weakness is youth and progressives. Latino support is OK but could be better. Harris is still the best choice for VP because she's a star with the resume to be president. Warren may boost progressives but has little appeal to PoC. Klobuchar is another Kaine would not inspire the Obama coaliton enough.
This could be more 1980 than 2004, as the economy falls apart (recession, high unemployment) due to the pandemic and Trump's bungling of it.
The lack of rallies etc and social distancing helps Joe and hurts Trump.
Basically I think Joe will win the GE the same way he won the primaries. It will seem as though he's running a weak campaign, then will suddenly spring back and win by a good margin.
But we're going to have to work hard, also on downballot races.
primary today, I would vote for: Joe Biden