PREP-197

Soaring television costs accounted for more than half the spending in the presidential campaign of 1992, a greater proportion than it was in any previous election.
A.    a greater proportion than it was
B.    a greater proportion than
选B. 解释里说这个句子中只是单个名词(proportion)的比较，所以不需要考虑than后面补出主谓，只补出介词短语就够了，不用担心后面的介词短语in any previou election没有平行对象。
为什么我觉得是介词短语比较，in the presidential campaign of 1992和 in any previous election？之前看到有个帖子说介词短语比较前后一定要有对应的介词短语，如果把题干中的 in the presidential campaign of 1992去掉，选B还对吗？

Although Napoleon's army entered Russia with far more supplies than they had in their previous campaigns, it had provisions for only twenty-four days.
(A)    they had in their previous campaigns
(B)    their previous campaigns had had
(C)    they had for any previous campaign
(D)    in their previous campaigns
(E)    for any previous campaign
选E，因为前面的复数指代都不对。请问这个句子中是什么和什么比较？我怎么找不到和for any previous campaign对应的介宾比较？还是我把介宾比较搞错了？恳求好心人解释一下！