In an inside baseball letter from Joe Biden to Dem bigwigs, telling them to give him just a bit more time, Joe Biden appeared to lay out his main strategy:
Ride Obama's coattails. That and the "optimism" angle appear to both be directly lifted from watching the first debate.
Serious debate analysis that wasn't there to fluff Hillary Clinton noted how all five candidates tied themselves to Obama to some degree. Clinton was surely No. 1, followed closely by Martin O'Malley, with Bernie Sanders a somewhat distant third.
Biden seems to have that as a natural temperament. Clinton may have it to some degree, but she's long ago locked it up, and I don't think Sanders really has it.
Biden would still have a huge uphill sled, and need to find some "his own man" ideas, but, some of those, he'll already have.
His "push" of Dear Leader on gay marriage and his "big fucking deal" on Obamacare will surely both get mention. And, Obama already gave Biden his blessing, and hinted about a possible endorsement. It won't be Clinton, if both are in the race. Not that I see. Have you heard Dear Leader utter one word about her email imbroglio?
Otherwise, yesterday, Obama continued to walk a tightrope between the two. But, that's with Biden not (yet) in the race. In additional video at that link, insiders say that Biden is not worried about his "legacy" if he runs and loses.
I still think that, after Tuesday's debate, he's more likely to sit out than jump in, but time — just another couple of weeks' worth at most — will tell. Other than that general thought, from my gut and intuition, no way I'm offering percentages.
It should be noted that, if Biden doesn't run, and a GOPer wins the 2016 general, Biden 2020 would be older than Sanders 2016, which is old indeed.