Complex sentence: Most Kentuckians, including residents of Louisville, voted for John Bell of Tennessee, of the Constitutional Union Party, which stood for preserving the Union and keeping the status quo on slavery or Stephen Douglas of Illinois, who ran for the Democratic Party ticket.
Split into simpler sentences: Most Kentuckians, including residents of Louisville, voted for John Bell of Tennessee, of the Constitutional Union Party. It stood for preserving the Union and keeping the status quo on slavery; others voted for Stephen Douglas of Illinois, who ran for the Democratic Party ticket.