he's got to make the filing deadlines as they come up. They begin to do that in early/mid November, his handlers won't want to wait until the last day to get their ducks in a row. I suspect he'll announce a decision around the end of the month.
The polling hasn't made it easier for him to come in. There's been at least a brief hiatus in the fall of Clinton polling numbers, and Sanders numbers have at least gotten very noisy, they may be showing signs of topping out in the low 30's. So the necessity of coming in as an establishment saving substitute isn't as strong, and his coming in actually could make the anti-establishment candidates position look stronger.
If Biden comes in it can't be as a threat to Clinton without really disrupting the democratic right. There is no sign that H> surrogates and supporters are ready to welcome him, even if Clinton is publicly working to look neutral. The bad joke, laid out on the ground like a gauntlet, is Biden hasn't yet found an announcement speech to plagiarize.
What Biden undoubtedly has done, is demonstrate that he's a credible back-up. He's reassured the Establishment there is a neoliberal friendly alternative to Clinton. That works not only within the campaign for the nomination, but also for the last year of the administration. Obama can move forward reassured there will be a balance to anti-corporate campaign rhetoric with a prospect for a new president who will continue along a similar path.
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