I know that part of the lead up to the American civil war was the fear of more non-slave states joining the union, but did southern states ever think of splitting themselves specifically to gain more pro-slavery senators and congressmen? For instance, if Alabama split itself into East and West they could have essentially have 4 pro slavery senators instead of two, and maybe could have added an extra congressman or two if they split it right?
I see your thinking. However, lets look at a scenario. Alabama in had a population of 771,623 people in 1850. If Alabama split in two, you would have two states with 385,811 and 385,812 roughly and had 7 seats in the House. Now lets look at a comparable state Michigan in 1850, MI had a little over 390,000 people in 1850 but only had 3 seats. So in the House Alabama's 7 seats would probably be split between these two theoretical states. Now for the Senate remember it is not a total for 4 extra seats but a gain of 2 extra seats. If you split a state there are only two additional seats created. Now I've never heard of a legitimate discussion of southern (future confederate) states splitting themselves. Why because you need Congressional approval and approval of the state legislatures involved. See Article 4 U.S. Const. So even if the southern states wanted to they would need to get northern state congressional delegations approval which wouldn't happen.