I see the GOP being the dominant Party in the US for decades to come

[🐒Gods of Prosperity🔱🐲💸]

There is pretty much nowhere left for Republicans to permanently gain white voters. They aren't going to ever win more than 60% of the white vote in a presidential election barring an unusual landslide.

I doubt Mitt Romney is going to be the upper limit.

[🐒Gods of Prosperity🔱🐲💸]

There is pretty much nowhere left for Republicans to permanently gain white voters. They aren't going to ever win more than 60% of the white vote in a presidential election barring an unusual landslide.

I doubt Mitt Romney is going to be the upper limit.

Do you think the Democratic candidate being African-American rather than white—as the 2016 nominee will be—might be a factor in Republicans' record performance among white votes in 2012?

Yes, it might have been a factor - but one that was pretty much already in the 2008 recipe. Mitt Romney was not a great candidate.