What led to the demise of the Whig Party?

The Whigs could no longer agree on a position for the slavery issue. Whigs began joining the Republican Party if they were against the preservation of slavery and the Democrats if they were for keeping it as a state option. By 1856 there were not enough Whigs left to have any chance of electing a president, although they did run a coalition candidate , Fillmore, who got 22% of the votes.