That’s because Joe Biden has maintained good relations with Senate Republicans, and average Republicans either are fond of him, while not being supporters so much, or just don’t take him seriously. Rush kinda convinced his fans that Biden’s a fool. But that’s a charge that would never stick because you put him on a debate stage and it’s clear he knows his stuff. Gaffes aren’t what they used to be in politics.
There will be a negative campaign against Biden, and it will probably be the same playbook both Republicans and Democrats used against John McCain: too old, too impulsive. At least he won’t have GWB hanging around his neck like McCain did. Obama is a much easier burden to carry and he’s not directly succeeding Obama.