Answer:
1. Illinois
2. Stephen A. Douglas and Abraham Lincoln.
3. The Issue of Slavery Extension
Explanation:
In the course of seeking for senatorial seat, both Democrats candidate Stephen A. Douglas and the Republican counterpart Abraham Lincoln went into series of debates in 1858, to argue the Issue of Slavery Extension in new Western states (New Mexico, California, and Texas).
The debates which was convened in seven different places includes Ottawa, Freeport, Jonesboro, Charleston, Galesburg, Quincy and Alton.
Hence, in 1858, the two candidates for US Senator from ILLINOIS were STEPHEN A. DOUGLAS and ABRAHAM LINCOLN. In their campaign debates, they argued about THE ISSUE OF SLAVERY EXTENSION in new western states.
