Donald Trump is potentially different. With him you really do see the potential for non-hyperbolic apocalypse. Shooting off nuclear weapons at random countries, refusing to respect the rule of law ... he is the first serious presidential candidate in my lifetime who genuinely threatens the fabric of American democracy (and, in its way, global stability, since a destabilized American democracy would also be a global catastrophe).
And if that is the case -- what a stupid way to go! All great powers eventually decline, but one would at least hope that America's would be a little dignified. But the history books about Trump's ascendancy would have to conclude that the greatest, most powerful country in the history of the planet unraveled because it couldn't tolerate someone from the wrong ethnic group being president and decided to throw a collective temper tantrum by electing in the most absurd overt demagogue possible.
Most Democrats continue to think Donald Trump is unelectable come November. I'm inclined to agree -- the case of candidates like Sharron Angle and Christine O'Donnell in the otherwise-GOP-wave year of 2010 indicates that enthusiastic Republican fury manifesting in the nomination of crazy turns off most American voters even in environment's broadly favorable to the GOP -- but who knows? It's all fun and games until somebody gets elected.