Slate is far from a partisan mouthpiece. For those that were too young to remember, here's an article that revisits Joe Biden's plagiarism. This piece is an in-depth examination of the offenses and why they were particularly important at that juncture in time, as well as today.
As I have said repeatedly, Biden brings experience that Obama just doesn't have and will not get before November. But with that experience comes the deeds of a career politician, some already known and others, yet to be discovered.