A Biden candidacy would not have the same effect. His base of support would be remarkably similar to Hillary Clinton. Biden, also a product of post-1960s Democratic politics and someone who is closely tied to the current administration, would promote a very similar set of themes as his chief opponent.
The result would be a bitter campaign that could quickly veer into personal politics. Rather than a competition to broaden and energize the electorate, this would be a campaign about dividing constituencies. It would sew intense bitterness within a Democratic Party that right now should be starting to focus their excitement behind a candidate and targeting their anger toward the GOP.
A Biden candidacy would also accelerate the campaign spending wars since Clinton would face much stiffer competition in key primary battleground states where Biden is likely to have strong appeal. The problem of money and politics has already been a huge one for both parties. It is difficult for Democrats to appeal to the middle class when they engage in campaign fund raising and Super PAC politics with rooms full of one percenters.