Isn't it amazing that Biden is thought to be the strong, establishment alternative. Have we all forgotten what a gaffe machine the man is?
Well, Hillary hasn't been doing so great. Biden is the only establishment alternative we've heard about, so he pretty much wins that by default.
If Clinton collapses and Biden makes a late entrance is as an establishment savior, then, in my opinion, Sanders becomes the front runner. Crazy, I know, but what's the alternative? Biden has no natural constituency and excites nobody. Hillary isn't about to drop out. In that scenario, we assume Clinton's donors switch to Biden, but she already has enough money to run a campaign through New Hampshire, and she's not just going to drop out. If Biden gets in and gains traction, Sanders will start topping national polls.