Biden is reportedly "convinced he can beat Trump", but remains uncertain about pulling the trigger:
I wouldn't if I were Biden. He's literally one of the most obvious possibly candidates for a #MeToo scandal to occur during the race.
I also doubt he would gather much enthusiasm (among white non-educated, among millenials, among black voters, among hispanics, among females and among progressives), and he also has too much history and is too affiliated with the establihsment... He'll probably still win, but he's not a strong candidate, and Trump has a shot of beating him... I also believe compared to other democrats Biden will do worse in the rust belt. The democrats need a candidate who will win back the Rust Belt and win disenfranchised voters back, and Biden isn't a good option for that. Though Biden would do well in Arizona, North Carolina and Florida, because he'll probably win some independents / moderates and conservatives, and have a larger share of older people than other democrats.