You can read about the new AP / IPSOS poll here. Here are the national numbers:
Giuliani 26 Huckabee 18 McCain 13 Romney 12 Thompson 11
Note that the frontrunner is ahead by eight points, while only seven points separate the second-place candidate from the fifth-place candidate. Huckabee's rise in Iowa has led to a volatile national swing, in which Thompson's national support retreats as Huckabee surges from out of nowhere. The swing happened rapidly. Who's to say we're not due for one more swing, or perhaps two more, before January 3, 2008?