Cilizza notes:

Another interesting finding from the Newsweek poll is that there seems to be a massive age gap forming around the choice between Obama and McCain. Among voters aged 18 to 39, Obama led McCain 56 percent to 33 percent; voters 40-59 were essentially a wash (44 percent McCain/41 percent Obama) while those 60 years of age or older went for McCain by a 48 percent to 37 percent margin.

We all know which age group has historically voted most reliably, although Obama's primary performance suggests he can change that pattern. 

--Michael Crowley