What political gains and losses did the Democratic Party's association with the Civil Rights Movement cause?

I would say that the association between the Democratic
Party and the Civil Rights Movement led to the situation we now have where whites (and
especially white men) tend to vote Republican (especially in the South) and where the
Democratic Party is the party of almost all
African-Americans.

Although the Democratic Party was not
particularly pro-Civil Rights at first (because of its heavy Southern membership), it
came to be associated with the movement because of the efforts of the Kennedy and
Johnson administrations.  This helped cement its popularity with black voters (which had
started in the New Deal).

However, the association hurt the
Democratic Party badly with white voters.  It allowed Nixon to use the "Southern
Strategy" in 1968 and 1972 and it helped Ronald Reagan win the South in 1980.  Nowadays,
the South is solidly Republican -- a move which started with the Civil Rights
Movement.