Sentence:  His strong opposition to the transfer of Negro children to schools outside their own neighborhood , in the interest of integration , will be attacked by Negro leaders who have <WSD>fought</WSD> for , and achieved , this open or permissive enrollment . 
Meaning of the word marked with <WSD> tags:  exert oneself continuously, vigorously, or obtrusively to gain an end or engage in a crusade for a certain cause or person; be an advocate for