求教2道语法句子主干题

题目是LZM-E8-7题,没有看懂句子结构:

During Roosevelt's years in office, Black Americans began voting for Democrates rather than Republic in nations elections,but Black support for Democrats at the state and local levals developded only after when civil rights legislation only after Harry Truman's support of civil rights legislation by Harry Truman.

这句完全没有看懂,急切求教各位大虾!

能把题贴出来么

BA began xx, but b suport xx after xx.

after when是重复的表达方式。