Other polls, such as the respected Mason-Dixon (which is a quality pollster in the South), has shown Bredesen+3.
...3 months ago.
Not much has changed to affect the race since May, though. There was a string of polls in April and May that all showed Bredesen ahead, and since then the national environment has only become more D-friendly and Blackburn has done almost no campaigning or ad spending. Unless Trump's endorsement caused a 17-point swing, there is no reason Blackburn should be up by this much, even if the older polls overestimated Bredesen's strength.
