You should make a note that in 1948 Strom Thurmond had the Democratic ballot line in Mississippi and in 1964 Goldwater had both the Democratic and the Republican, while Truman and Johnson were on third-party ballot lines. So someone who checked the box to vote for a straight Democratic ticket would have voted for Thurmond or Goldwater.
I never really though of that actually. The fact that Goldwater was on both the Republican and Democratic ballots in Mississippi might have inflated his actual level of support by about 10-15 points.
