This ABC News/Washington Post poll was conducted by telephone Dec. 15-18
In other words, Thursday through Sunday.
The CNN poll showing little or no improvement was taken Saturday and Sunday.
Thursday was when we were being inundated with footage of joyous Iraqis holding up their purple fingers. Friday was before most people had heard of Spygate. By the weekend, the Iraq elections were old news and people were starting to hear about the domestic spying.
I'd be curious to see the variance over those four days. I wouldn't at all be surprised to see Bush's ratings going steadily downhill over that period.