Just a reminder

Unless you count the poor, immigrant labor exploited by Industrialists in the North long before Mexico ever came into the picture.

Yeah that's why democrats aren't the party of slavery

How's that, because of the "Big Switch?" You mean Irish labor wasn't exploited similar to other immigrants during that time? What about the first Democratically Elected Democrat Party President Andrew Jackson, author of the Trail of Tears who was a stark racist if ever there was one towards just the Cherokee alone? And you say they weren't in favor of slavery... THEY VOTED FOR IT BACK THEN!!!

It's because the party was torn in half over slavery. There was a northern democratic and southern democratic presidential candidate in the 1860 election.