The cavernous power vacuum on the left caused by unchecked capitalism/corporatism (corporate personhood) caused all of the fiscal conservatives in the GOP to leave the circus and take over the DNC (look into the “Democratic Leadership Council” headed up by the Clintons and their right wing buddies).

You can't just leave that at the feet of the electoral system. The cavernous vacuum was the direct result of domestic intelligence, surveillance, and disinformation campaigns organized by the federal government to undermine any organization that threatened the white supremacist state structure dominant during the 60s and 70s. The Cold War wasn't just something Americans fought abroad. It came in the form of political assassinations (Fred Hampton, Malcolm X, and MLK). It came in the form of corporate strike breaking efforts on a national scale. It came in the form of paramilitary operations - the MOVE bombing in Philadelphia was a classic example, but SWAT raids and police harassment efforts stretching from California to Florida helped break down the nascent counter-culture organizations post-WW2, while the CIA-fueled crack epidemic and lead paint/gasoline fumes and other ecological catastrophes demolished the mental capacity of a generation.

Left wing organizations and movements didn't just vanish, they were systematically uprooted and destroyed. The modern fascist state and municipal governments we live under are the direct result of policies implemented generations ago. The electoral system is as much a victim of that violent manipulation as anything else.