Does your scheme make any assumptions about the number of GOPs voting for Obama and the number of Dems voting for Romney?
This is important. If the answer were, for example, 50% of Dems vote for Romney and 50% of GOP vote for Obama then the mix of Dem to GOP doesn’t matter. If the answer is GOP and Dem loyalty is 100% then you should be able to just add the percentages in your head.
Now neither of these extreme cases is true but the number you choose is important and needs to be declared and to be part of the calculation - even if it’s 95% party loyalty.
I don't know if Leto's calculations do so, but the blogsite he cited does make those adjustments.
“Does your scheme make any assumptions about the number of GOPs voting for Obama and the number of Dems voting for Romney?”
In my personal spreadsheet I do.
In polls where they give the internals they will say have 90% of dems voting for O, 4% Romney and 5% undecided. they reverse for Romney. The turnout model is then applied to the % for each party and the independents.
It looks like the blog works with the raw numbers for the polls.