My take on it is that these people, for the most part, are seeing the effects of the shadow movement, and are losing their faith that any one president or congress ever can change the way things are going.
One interpretation of the poll is:
The Washington Post-ABC News survey found that less that half of Americans — 49 percent — say they believe the president will make the right decisions for the country. That's down from 60 percent at the 100-day mark of the Obama presidency.(Yahoo AP News, [moved, so see this]). Posts on this blog a while back postulated that the advisers had forgotten that the election was a rejection election, and that such a miscalculation would lead to the talk of change but a continuation of the policies that were rejected in the election, and ultimately to another rejection of those policies:
It is time to bring some wrath down on the ideology and the perpetrators of the ideology that was rejected in our recent election.(Dredd Blog, 3/31/09). It has not reached the 20% drop from where it was on March 31, well before the 100 day mark, but it is getting there fast.
If that does not happen, the damage that will be done as a result of that failure will not go unnoticed. I expect a 20% drop in popularity when all is said and done.
Dredd Blog also pointed out that President Obama inherited pure hell and that in and of itself would limit what he could do even if he set out to totally comply with the will of the people.
That said, if the Obama Administration continues to think it is all about the personality of Obama so that he can continue the policies of Bush II, the 20% drop may end up being overly optimistic.