For all the Media excitement about a possible Joe Biden run for President against Hillary Clinton (I don't think there really is much excitement for a Biden run in and of itself), the reporting actually seems to indicate that Joe Biden understands he is Plan B:
Those who have spoken directly to Mr. Biden, who spent part of this week with his grandchildren in Delaware, increasingly believe that he is going to take several more weeks to decide whether to pursue a candidacy. They hope the time will provide more clarity about how much political damage Mrs. Clinton has suffered as a result of the email issue, and whether the problems will last. [. . .]
“He’s not unrealistic that if she’s able to right the ship here, at this point it’s tough, really tough, to see a lot of Democrats coming off her,” said one former senior Obama administration official who recently discussed the merits of a campaign with Mr. Biden. “On the other hand, the things with the emails and everything else could deteriorate — who knows? So I think he’s figuring he’s got another month or so to see what happens, to sort of put feelers out there.” [My emphasis]
This is realistic. For Biden to have a chance, Clinton has to implode. He is Plan B. But I would go further, as Plan B, Biden doesn't really need to have a timetable. If Clinton implodes, Biden will be the inheritor of her support, at least initially. Hes have a reat chance to become the nominee.
This actually would be the best scenario for a Sanders win imo. But also Nate Silver's:
How can Bernie Sanders win? [This is an edited transcript of a conversation in Slack.]
natesilver (Nate Silver, editor in chief): I still think it needs to involve some “shock” (as an economist would define that term) to the Clinton campaign. Meaning, some substantially worse turn in the email scandal than what’s been reported so far. Hackers publish a bunch of top-secret documents culled from Clinton’s emails, for instance. Or a new scandal. Or a health problem.
In that event, Democratic elites would probably turn toward another establishment candidate. Most likely Joe Biden. But while I’m pretty sure that Sanders can’t beat Clinton head-to-head — he’s losing to her badly now, after all — I’m not so sure that’s true of Biden, etc.
I think Sanders vs. Biden, in a world where the Democratic establishment is in disarray because of a Clinton crisis, could be highly competitive. And Bernie’s organizational advantages — e.g., in the caucus states — could help him against a candidate who is getting off to a very late start.
That sounds right to me too. I'm not sure any other candidate is really a factor or can be.
It's Clinton or Biden (Plan B) v. Bernie. And Bernie would have a much better chance against Biden than Clinton.