Why was the 1968 election a turning point in US political history?

A.
It saw the end of the New Deal coalition.
B.
It saw the first important third-party candidacy.
C.
It saw the Republican Party become dominated by eastern moderates.
D.
It saw the South swing to the Democratic Party.

Explanation:

The 1968 presidential election took place against civil unrest and tragedy, following the assassinations of Robert Kennedy and Martin Luther King Jr. Race riots and the ongoing Vietnam War had shaped public perception negatively against the incumbent Johnson administration.

it was on the rise and doing very well and would continue to do well until the great depression from 1929-1939