When Mississippi voting registrars refused to recognize their candidates , they held their own primary .
In 1964 , organizers launched the Mississippi Freedom Democratic Party ( MFDP ) to challenge the all - white official party .
When Mississippi voting registrars refused to recognize MFDP 's candidates , MFDP held their own primary .
In 1964 , organizers launched the Mississippi Freedom Democratic Party ( MFDP ) to challenge the all - white official party .