Paul Krugman, responding to He Who Shall Not Be Named*, lists some of Ronald Reagan's "innocent mistakes," all those hilarious instance when the trusting, well-intentioned conservative icon accidentally adopted positions, legislative priorities, and personnel strategies that just happened to accord with what hardcore Southern racists -- and Reagan's new white, Southern, base -- wanted.
In any case, to go back to the original argument, Reagan's speech in Philadelphia, Mississippi may or may not have been placed there as some sort of dog whistle. But when Reagan went to the South and began talking about States' Rights, let's not pretend any of us are naive enough to miss the intended resonance. Reagan probably wasn't, himself, a racist, but he was very interested in attracting the votes of those with, shall we say, retrograde views on the subject. And that came out not only in his rhetoric, but, as Krugman shows, in his policies.
*David Brooks