Well, here's Gordon Brownwell's letter to Harry Dent. Dent worked for Strom Thurmond, Goldwater, Nixon, Ford, Reagan, and George H. W. Bush.
Here's Strom Thurmond who stumped and strategized with the Goldwater and Nixon campaigns (excerpt written by former Republican Congressman Paul N. McCloskey, Jr.) https://www.huffpost.com/entry/republican-convention-1968-2016_b_9574256
Here's Kevin Phillips who worked for Nixon (excerpts from Venomous Speech: Problems with American Political Discourse on the Right and Left) https://www.amazon.com/Venomous-Speech-volumes-Political-Discourse/dp/0313398666
Here's Lee Atwater, who worked for Reagan and George H. W. Bush https://www.bradford-delong.com/2017/03/lee-atwater-interview-with-alexander-p-lamis-rough-transcript-weekend-reading.html
And more on Atwater (who was working with Roger Ailes of Fox News and Roger Stone) from my own book, The Long Southern Strategy https://www.amazon.com/Long-Southern-Strategy-American-Politics-ebook/dp/B07RWP3D3V
Here's Paul Manafort, who ran Reagan's southern campaign and, of course, worked for Trump before going to prison. You can read more @facingsouth https://www.facingsouth.org/2017/11/paul-manaforts-role-republicans-notorious-southern-strategy
Here's Ken Mehlman, former RNC Chair apologizing for it all... https://www.nytimes.com/2005/07/18/opinion/an-empty-apology.html