There is one party with 2 names. The diff between the factions are the issues they use to whip their constituents up into a frenzy, to vote for them and against their own best interests. They pretend fight the other side, keep their bases in survival mode to deflect attention away from the reality they're both fighting for special interests and their corporate backers.
Then genius of this strategy is no matter how bad they fuck up, how bad you are treated or how bad your condition gets, they will tell you the only solution is to stay the course and vote for more of the same because *insert name* is worse than them. The 'opposition' will run someone worse if that's what it takes to sell it.
And it works. Most people believe the illusion.