Goldwater sent blacks to the Dems at a much faster pace than was the case with the new deal. Goldwaters being against the civil rights act of 1964 was the main reason for white southerners to go Republican. And for blacks all over the nation to be Democrats. 1964 Goldwater was a pivotal mistake for the Republican Party.
So the "mistake" by Goldwater caused white southerners to go Republican placing the electoral votes of Texas (36), Florida (29), Georgia (16), North Carolina (15), Tennessee (11), South Carolina (9), Alabama (9), Louisiana (8), Mississippi (6), and Arkansas (6) into Trump's column and not Hilary's.
And that is bad how?