Sure, google-fu the term "Romney won the white vote" and that will start you off. I believe I read somewhere that Romney won a greater share of the white vote than did Reagan, but I haven't verified that.
There have also been numerous pieces of analysis which note that it will be easier for Republicans to peel off a 1% white vote from the Democrats than to get the same number of Hispanic voters but needing to capture 5% in order for the voter totals to be equal.
Lastly, it all boils down to policies. From whom will the money be extracted and to whom shall that money be directed. Obama has put Affirmative Action into many places in the ObamaCare legislation, it's now in the Financial regulations. These hiring quotas will only increase.
Look at what happened in Texas in the Fisher AA case - the U of Texas wanted to grant Affirmative Action to the children of rich Black and Hispanic professionals and disadvantage the children of white working class parents who outscored them in grades and SATs.
This race-based stuff will only increase in scope as the country gets more multicultural. Even the white political leaders and operatives in the Democratic Party are going to be squeezed out eventually - it will become impossible to run a plantation like political system - white leaders and staffers lording over the brown mass of voters. There are ambitious people in that brown mass of people and they're going to want to be leaders. How much longer do you think that this is going to be
possible:
As you can see here, beyond Cory Booker (who faced a real race in October but as of now has no real opponent), not only are the Democrats running a virtually all-white slate of candidates in the marquee statewide races, just about every Democrat in a hotly contested race this year is white.
One last point - Pew ran a poll recently which asked Young Millennials whether they wanted to increase the scale and scope of government or reduce it. The vast majority of white respondents thought government was too large and doing too many things and should be scaled back. Minority voters thought government was not going enough to help them and wanted to increase the scale and scope of government operations in society.