No Democrat has won the majority of the white vote since 1964, when Lyndon Johnson signed the Civil Rights Act. Of course it's about race.
Racism is the glue that held the country together. As long as both parties were a bit racist, we could build bridges and dams and highways.
When both parties were a little bit racist, government could do big things like Social Security, Medicare & GI bill on a bipartisan basis.
Shortly after the Democrats aligned with the civil rights movement in 1964-1965, government became the enemy for many white voters.
After signing the 1964 Civil Rights Act, Lyndon Johnson reportedly told Bill Moyers that Dems would lose the south for many years to come.
Nixon exploited white fears with his "southern strategy" in 1968. Reagan used "states' rights" & Cadillac-driving "welfare queens" in 1980.
George W. Bush used "Willie Horton." Newt Gingrich used "food stamps." And all Donald Trump had to say was "make America great again."