I can do math too - what should Romney have gotten if you take the population growth into account?
Growth in the electorate is 4% from 2004 to 2008.
It would be quite the stretch to suggest that ANY of the base is part of that electorate growth, given that the fastest growing portion of the population is Hispanic.
And I don’t think 18-22 year olds in general are part of the “base” that “stayed home.” Do you?