It is biased, but not intentionally. This happened during the campaign too. There were some results that oversampled GOP too. It was not just Dems. The problem is the methodology seems to have evolved to be flawed -- Even Though It Hasn't Changed Over The Years.
For some reason random samples grossly oversample one party vs the other at different times. If I had to bet on what's happening now, I would bet that GOP voters have already become bored with Katrina and are not at home watching TV waiting to be polled.
It is intentional.
Dick Morris would call the NY Times and ask them to run a poll to help Bill out in 1996.
Newsweek, the AP, Zogby, CBS, NY Times depend on FAKE POLLS to justify their news coverage.
Since Bush is not running for office again, they can do whatever they feel like and their will be no referendum to debunk it.
2004 was a clear case of FAKE POLLS. It was limited by the 'likely voter' sample which liberal news orginations had to follow.
The many who got it wrong in 2004, did so by oversampling Democrats and undersampling Republicans.
It was as intentional then as it is now.