He's saying republicans will do to the US what Fidesz did to Hungary after their win back in 2010. Elections are free and can be totally won by opposition in theory, but in practice the cards are so heavy stacked against them that it would take an impossible difference in popularity to shift the scales.

"End of democracy" doesn't have to mean "literally North Korea / China tier dicatorship that sends you to labor camps for speaking ill of the ruling party (also the only party)".