From Rasmussen Reports:

In the final full month before Election 2006, the number of people identifying themselves as Republicans has fallen to its lowest level since we began reporting this measure of partisan trends in January 2004. As a result, Democrats have their biggest net advantage of the past two campaign cycles.

This information confirms what we see in the congressional generic ballot that currently gives Dems a 15-point advantage in the RCP Average. Today's NBC/WSJ poll shows similar results:

Voters want Democrats, rather than Republicans, to control Congress by 52% to 37%, a 15-point margin. The spread matches the widest ever recorded on this question in a Journal/NBC poll.

There is no question that as we get closer to the election the generic ballot takes on added significance, however the huge unanswered question is just how much this tells us about which party will win the Senate and the House? At the end of the day, this isn't a national election but rather hundreds of individual races where 3-5 contests in the Senate and 20-30 contests in the House will ultimately decide who "wins."