[GOP_Raider]

Then why didn't they secede in 1859?

Or what would have happened if John C. Fremont had won the presidency in 1856 instead of James Buchanan? Would much of anything have been different or would his administration, presumably setting as policy the expansion of slavery, have hastened the inevitable southern secession and Civil War?

[Non-Sequitur]

Or what would have happened if John C. Fremont had won the presidency in 1856 instead of James Buchanan? Would much of anything have been different or would his administration, presumably setting as policy the expansion of slavery, have hastened the inevitable southern secession and Civil War?

It may well have. The 1856 Republican Platform contained a plank against the expansion of slavery in the territories.