Lincoln Douglas debate letter

[Steve]

In December, Christie's is auctioning off this 1858 letter while preparing to debate Stephen Douglas. Did the debates between Douglas and Lincoln help break apart the Democratic Party in 1860 as the description claims? I know, contrary to what it says, Lincoln would've won the Electoral College vote even if the Democrats hadn't split.

http://www.christies.com/lotfinder/books...tails.aspx