I don't understand how these odious characters on both sides continue to get elected
Its easy. There is a certain percent of the population that will vote Democrat or Republic regardless of who runs.
And in some voting areas, the Democrats or Republics are far in the majority, so the result is known before the voting starts.
The incumbent already has a built in 20-30 point advantage.
DOnt know if you makes you feel any better, but it is the same in Taiwan and other countries.