Abraham Lincoln's and the Republicans' political platform in 1860 was to stop slavery's expansion. Historian James McPherson says that in his famous "House Divided" speech in 1858, Lincoln said American republicanism can be purified by restricting the further expansion of slavery as the first step to putting it on the road to 'ultimate extinction.' Southerners took Lincoln at his word. When he won the presidency, they left the Union to escape the 'ultimate extinction' of slavery."