Trying to pinpoint the "party switch"

The theory goes something like this:
"The Democrats used to be racist. But they switched parties, and now the Republicans are racist."

Ok. When?

When did this happen? I realize that these things would necessarily happen over time, but when did the racists migrate from the Democrat party to the Republican party?

Take, for example, a well-known Democrat who was part of the KKK and the "racist" Democrats before the alleged "switch". Robert Byrd has held continuous national public office for the state of West Virginia from 1952 until his death in 2010. If Robert Byrd "switched" on racism, but never switched parties, how is that possible?

We can assume that a single man might have a eureka moment in which he suddenly and completely switches beliefs about a subject like racism. But can a whole state, like West Virginia, switch at the same moment?

And when did the entire state make that "switch"? Here's a short history of Robert Byrd's political and racial history. Tell me when you think the entire state of West Virginia changed on racism.

• Formed a new chapter of the Ku Klux Klan, early 1940's
• "Kleagle" for the KKK, 1943
• Wrote a letter stating, Byrd "shall never fight in the armed forces with a negro by my side." 1945
• Wrote a letter to a KKK "Grand Wizard", 1946.
• When running for office, Byrd lied and said he quit the KKK "after about a year", 1952.
• West Virginia's 6th congressional district, 1952:
• Robert Byrd (D) - 104,387 (55.58%)
• West Virginia's 6th congressional district, 1954:
• Robert Byrd (D) (inc.) - 73,535 (62.73%)
• West Virginia's 6th congressional district, 1956:
• Robert Byrd (D) (inc.) - 99,854 (57.40%)
• West Virginia United States Senate election, 1958:
• Robert Byrd (D) - 381,745 (59.19%)
• West Virginia United States Senate election, 1964:
• Robert Byrd (D) (inc.) - 515,015 (67.67%)
• Byrd personally filibustered for 14 hours against the Civil Rights Act of 1964.
• Voted against Thurgood Marshall's Supreme Court nomination, 1967
• Byrd "indicated it was time that [Martin Luther King, Jr.] 'met his Waterloo'" to the FBI, 1968, just months before MLK was assassinated.
• West Virginia United States Senate election, 1970:
• Robert Byrd (D) (inc.) - 345,965 (77.64%)
• Byrd was the Majority Whip, 1971-1977
• West Virginia United States Senate elections, 1976:
• Robert Byrd (D) (inc.) - 566,359 (100.00%)
• Byrd was the Majority Leader, 1977-1981
• West Virginia United States Senate election, 1982:
• Robert Byrd (D) (inc.) - 387,170 (68.49%)
• Byrd was the Majority Leader, 1987-1989
• West Virginia United States Senate election, 1988:
• Robert Byrd (D) (inc.) - 410,983 (64.77%)
• President pro tempore of the United States Senate, 1989
• President pro tempore of the United States Senate, 1991
• Voted against Clarence Thomas's Supreme Court nomination, 1991
• President pro tempore of the United States Senate, 1993
• West Virginia United States Senate election, 1994:
• Robert Byrd (D) (inc.) - 290,495 (69.01%)
• West Virginia United States Senate election, 2000:
• Robert Byrd (D) (inc.) - 469,215 (77.75%)
• Byrd refers to what he called "white niggers" on national television, 2001
• President pro tempore of the United States Senate, 2001
• West Virginia United States Senate election, 2006:
• Robert Byrd (D) (inc.) - 291,058 (64.41%)
• President pro tempore of the United States Senate, 2007
• President pro tempore of the United States Senate, 2009

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source:
https://en.wikipedia.org/wiki/Robert_Byrd
https://en.wikipedia.org/wiki/Electoral_history_of_Robert_Byrd
http://www.washingtonpost.com/wp-dyn/content/article/2005/06/18/AR2005061801105_pf.html
http://www.frumforum.com/remembering-robert-byrds-racism/