Romney won only 59% of the white vote to Obama's 39%.
The African American voter has been 8:1 or 9:1 Democrat since the 1960s. This is unlikely to change. However, let's assume that the group's voting percentage drops from 13% to 11%. Using 2012 figures, that means that there will be about 2.5 million fewer black voters, which, assuming a 89% Democrat support level (Gore won 90% in 2000 and Kerry won 88% in 2004) means 2.2 million fewer Democrat votes.
How would this translate in 2016 terms? Specifically, what would be the effects in the voting booths in Cleveland, Cincinnati, Columbus, Jacksonville, Tampa-Saint Petersburg, Miami-Fort Lauderdale, Richmond, Newport News-Norfolk? Small declines in black voter turnout can make a lot of difference in these purple states. I don't doubt Rick Scott in Florida will use the force of his office to keep the Democrats from cheating in Dade and Broward Counties, including cracking down on Northeastern "dual voters". I'm not so sure about Kasich, however. Virginia's governor is a Clinton crony, so we can assume Democrat ballot box stuffing will occur.