Jamelle Bouie writes at the Washington Post that if Mitt Romney had secured the same percentage of the African-American vote as George W. Bush, he'd be president today.
[H]igh African American turnout — coupled with average white turnout — means that black voters have an outsized effect on the popular vote, relative to their percentage of the population. This gave Obama a great advantage in last year’s election. Essentially, he could win by substituting new black voters for lost white ones. And that’s what he did. His popular vote margin in Ohio, for example, can be explained solely by higher black turnout.
The flipside of this is that Republicans can greatly improve their position in presidential elections by just winning more black voters. Without near-unanimous support from African Americans, states like Virginia and Florida become much harder to win for Democrats, while North Carolina falls out of reach completely.
Republican renewal starts by returning to the baseline.