SAT句子挑错题~

问题描述:

SAT句子挑错题~
A powerful advocate to equal rights,Belva (was) twice a candidate for President long before the Nineteenth Amendment to the Constitution allowed women to vote.
was为什么错了?

long before...did(allowed)出现了,肯定不能用一般过去时.
在allow前发生,用had been