Economy

They weathered the contentions Polk years (like the GOP weathered the contention Clinton years, although it cost them in the short term). What finally caused the collapse was the inability of the southern, pro slavery Whigs to reach any sort of compromise with the abolitionist northern Whigs. The collapse started in 1852, culminating in the disastrous 1856 convention, when the fighting was so fierce they failed to produce a presidential candidate.

Maybe history doesn't exactly repeat, but it certainly stutters a lot and I'm really hoping for a convention Donnybrook this year and for the same reason, a divide between the slave states and the free states.

Political parties that refuse to compromise internally or with the Democrats generally destroy themselves. I just want it in public and preferably televised.