Craig: I can talk to you about voting in Civil War Missouri. This is an untapped source on the Civil War
but there were five contested election cases for seats in the US Congress from Missouri namely:

John P. Bruce vs. Benjamin F. Loan 7th Cong. District

James H. Birch vs. Austin A. King 6th Cong. District

Thomas L. Price vs. Joseph W. McClurg 5th Cong. District

Samuel Knox vs. Francis P. Blair, Jr. 1st Cong. District

& my favorite: James Lindsay vs. John Scott 3rd Cong Dist.

All were written up in the Congressional Journals, and, tho' very boring they do contain data never found anywhere else. I recently gave a talk on the Lindsay vs. Scott case at the Fort Davidson Lecture Series and it is the one that holds the most fascination for me. For that reason, I have collected all five for my own library as well as Blair vs. Barrett in the pre-war and a few from the post-war. You will also enjoy the book: The American Ballot Box in the Mid-Nineteenth Century by Richard Franklin Bensel which contains quite a bit on Missouri.