My old boss at the McConnell Center, Dr. Gary L. Gregg, has an article on George W. Bush's dip in the polls on today's NRO. This was discussed to some degree at the conference on the Bush Presidency (which I still need to finish commenting on).

Dr. Gregg aptly points out:

Seldom does a president's crisis-induced popularity last longer than a few months and none has ever lasted longer than ten months. President Bush's rally is now over, but it took two full years to reach that point — shattering the old record and setting a bar it will be difficult if not impossible for any president ever to match.

...

The president cannot be happy to have an approval rating of just 50 percent a year before he stands for reelection. However, put into historical perspective, Bush's record-breaking popularity of the last two years was unprecedented and the current decline inevitable. And, as I am sure his advisers are reminding him, his current approval ratings mirror those of both Bill Clinton and Ronald Reagan at similar points in their first terms — both who went on a year later to handily win reelection.

I often find it amazing that most of the media, though not all, seems to miss this point. The media is so poll-oriented that it's strange that they don't report these type of trends more. However, it would probably help a President that most of the members of the press would never support and because of that they don't see it as news.