If there is a good scenario for Bredesen, it is that he ends up like Heitkamp in 2012. Nobody seriously thinks he wins, but then he somehow pulls it out in the end in an unexpected stunner after everyone has given up. That is the only way he wins. Nobody should actually be expecting him to win or thinking that it is likely. This is Tennessee we are talking about here, not some swing state, not even some lean R state, but Tennessee.
If the polls end up saying Blackburn is ahead, sure. But if he pulls ahead that won't mean we'll be expecting that he loses.