"Are you actually suggesting that the entire election nationwide should be re-envisioned based on a single poll?"
Sure, I have no dispute with that, other than to note that the claims are based on many months worth of both generic and specific polls.
I think the correct baseline when measuring states and districts is electoral performance in the 2000, 2002 and 2004 elections, maybe with a slight tinge away from the GOP based on the national mood, but nothing that would indicate that Democrats will suddenly becomedominant in districts that voted for Bush and the GOP House candidate in 2000, 2002 and 2004.
The Democrats have about twice as much money (proportionally) as they did in those other elections, so that alone is more than a "slight tinge" away from the GOP. In fact, by every factor up and down the line, including the aggregate polls, the Dems are in far better shape than they were in 2000, 2002, and 2004.
But, OK, let's say for the sake of argument that we did re-evaluate the entire nationwide portrait based on one poll. Which poll should we choose? Should we choose the 2% Dem margin (Gallup), the 9% Dem margin (CNN), or the 15% Dem margin (NYT) polled simultaneously? Oh wait, I almost forgot: The credibility of a poll is directly proportional to the desirability of the results.