Several times American political parties basically have destroyed themselves. Their destruction signaled a changed political landscape along with great and perhaps devastating changes within US society.
3 specific instances come me to mind:
1) the democrats in 1860 split over the slavery issue, vaulting the Republicans to power and causing the Civil War and Reconstruction and years of Jim Crow,
2) The Republicans in the 1930s turned a blind eye to the world's economic problems and pretty much watched the Great Depression and World War II from the sideline,
3) Democrats in the 1960s imploded over Vietnam and Civil Rights, allowing the rise of Richard Nixon and a constitutional crisis of the early 1970s,
Today it appears to be the GOPs turn again, internally splitting while the economy suffers and who-knows-what lurks…