Sentence Correction

I read somewhere, that prepositions must take the objective case and not the nominative case. I had made a note of this in my flashcard, however can someone tell me if this is true? I can't find the source right now...so your help will be appreciated.

Take the following for example;
"Every conservative except smith and she was defeated"
is the above statement correct as is ? or should it be "except Smith and She"...This doesnt sound correct if i follow the rule.

Another example;
"Everyone on both sides except the pitcher and me was injured in that game"- is this correct?

Thanks.

One thing that I know for certain is that we are allowed to use Objective case for pronouns only when they act as objects. Following this line, pronouns can act as objects only to two types of part of speecg: Transitive verba and Prepositions.

eg; " Ram kicked him" --> him is the object of the vern kicked; hence objective case.

eg; "Listen to me" --> me is the object of the preposition to; hence objective case.

This reasoning leads us to the answers:

"Every conservative except smith and her was defeated"

"Everyone on both sides except the pitcher and me was injured in that game".