The GOP has put themselves in a pretty deep whole as they pretty much have completely alianated younger voters. Now will they lose the young vote in the future by what they lost it in 08? Perhaps not, but they still have a long way to go.
As far as Mississippi and the differences between 04 and 08 go. Keep in mind that not all polls are perfect. You will generally have 1 poll out of 20 which is outside the MOE. So when you have a set of 50 exit polls, you will likely have 2 or 3 polls which are off by a bit. This appears to be the case in Mississippi in 04, and Maine as well
I think the GOP basically has to attract at least my vote in order for it to be successful in the future- something like a latter day Rockefeller Republican vote. They can certainly do it, but not with Sarah Palin, Jim DeMint, Rush Limbaugh and the wingjobs at the helm. Meghan McCain- absolutely (bonus- I like her curvier body!) though I don't agree with her on a few things still.
I'll be honest. It took GW Bush and the combination of Ed Rendell running for Gov to convert me from an Independent to a Democrat. There's a lot I'm not happy with in regards to local Democrats, but the national Republicans are just frigging out there.
