The Whigs collapsed in 1856, and the Democrats in 1860, because neither represented the views of the majority of Americans. American politics had been all about slavery since at least the 1830s, but both parties studiously avoided it. You could vote for the Whigs, who stood for nothing but not being Democrats, or you could vote for the Democrats, who were pro-slavery but wouldn’t admit it under torture. The Dems were better at coalition building some things never change and were able to cobble together the “Hard Shell,” “Soft Shell,” “Barnburner,” etc. factions together for one election longer than the Whigs were, but when faced with a legitimate protest party, they too collapsed. Their vote split several different ways, Lincoln won the White House, and I forget what happened next.
Today’s Republican leadership, in case you hadn’t noticed, stands for nothing but not being Democrats. And anyone paying attention knows the Democrats’ poster child: it’s a nonwhite female college student who will do anything to not get pregnant, but she won’t do that. (Or rather, she won’t not do that.) I can’t wait for the grownups to start running the playground again.