Why is Biden waiting so long?

Rumors continue to swirl that Vice President Biden will soon be (finally) making up his mind about whether to run for president. Why is this taking so long?

Conventional wisdom seems to revolve around two theories: (1) He really hasn’t made up his mind, or (2) he’s simply waiting on standby in case something big drops on frontrunner Hillary Clinton. Either is plausible, although the first strikes me as less plausible. If nothing else, Biden is a canny politician, and he understands the difficulties of entering the race this late in the game. I don’t think he’d simply wait around this long without a good reason.

So let me explore a third possibility: Biden is simply intent on avoiding the errors that plagued previous late entrants. If he does end up running, I’d say this was certainly the case.