Tennant has damaged herself significantly.
Really? Other than excessively distancing herself from Obama (which may not be a bad move in WV to be honest), what missteps has she made? I got the impression that while she's still a lock for defeat unless something major changes, she's been running a pretty great campaign.
Her excessive distancing herself from Obama has hurt her both ways - the Democratic base has no enthusiasm, and the center and right simply don't believe her.
You have absolutely zero evidence of this so, until you provide some, we'll move along.
What do you thinks changed? The polling clearly shows that somethings different.
So you're basically assuming Tennant is damaged because of one poll? Even if this poll were accurate (let's not discuss Rasmussen, but suffice it to say that West Virginia has been under polled), there could be a multitude of explanations for Tennant's troubles. Saying that she's imploding because of her distancing herself from the President is pure speculation on your part.
