The generic ballot predictions are increasingly irrelevant. One reason is obvious. Voting is already underway. Another reason is that a single partisan measure cannot predict the results in 435 House elections.
But the third reason is less understood and discussed after the fold.
Democrats are building their firewall!
The US is still a very imperfect democracy. States differ in their electoral practices and in their power arrangements.
In the blue states, labor, minorities, and the cellphone nation are now expanding the Democratic electorate. The generic ballot often does not register local mobilization. Red states are red partly because unions and allied organizations are too weak to energize Democratic constituencies.
Sestak is doing much better because of labor mobilization. And other Pennsylvania Democrats may also do well. This process is being duplicated in many other blue states. This means that so called unlikely voters are turning into likely voters.
In 2008, Democrats coalesced in Florida and North Carolina. Those states are a little more difficult to mobilize this year. But the AFL-CIO is probably expanding the voting population in dozens of House districts!
Most of the pollsters and pundits don't believe this is possible. If you say you're not sure where to vote you are ruled "unlikely!" Funny thing: the AFL-CIO and other Democratic groups remind you where to vote!
We may keep the House and maybe mainstream pundits will choose to doubt the Democratic electorate less in the future.