I think Biden and Mayo Pete are bad in a "please don't vote for them" sense. There are other candidates I don't love but I suspect people who vote for them aren't doing so because they are dumbasses, mostly, they are doing so because they have different priorities than I do and different (of course wrong because I am always right, but not necessarily wrong, because actually I am not always right) beliefs about unknowable things. "Who is more electable" or "how, exactly, will they govern," or "can they actually accomplish anything as president, more than the other person" or "will they appoint Rahm Emanuel Chief of Staff and send Timothy Geithner to Treasury?" are all basically unknowable things which people can have smart opinions about but they are just opinions.
And also people often have really dumb opinions about such things, and I don't mean "opinions I disagree with."