You're correct, but the positive poll results didn't go unreported. I remember the press making frequent note of Bush's very high poll ratings after 9/11. Not every third day, but the numbers weren't as volatile.

It's true that on all topics, not just politics, the press tends to find bad news more noteworthy than good news. I think it's partly the bias of people to be more concerned with news of potential danger or problems, to get some kind of advance knowledge of what's to come, than the good things that by definition aren't threatening. News provides situational awareness, and our jungle-trained senses let the good recede into the background so we can keep an eye on the bad.

The perceptual ground state of human psychology is that it's normal for things to go well, and problems are exceptions to be highlighted. Maybe the news focuses on the bad because people tend to be sunny optimists? The definition of "news" is that it's what's exceptional, so maybe it's good news that it's not news when things go well. Wouldn't you worry if the lead story on the evening news was "Thank God! Something went right today!"?