You've got at least six parties that I can identify:
1) A middle of the road European Social Democrat party (Bernie Sanders)
2) A centrist (or centre-right depending on where you're comparing it with) party (Hilary Clinton)
3) A right-wing-religious party (Ted Cruz)
4) A hard-right-verging-on-fascist party (Donald Trump)
5) Greens (They do exist, apparently)
6) Libertarians (Likewise)
Plus, presumably, the usual smatterings of Communist, Socialist, Pirates, etc. that crop up everywhere.
The problem being that right now, because of the two-party system, everyone gets pushed into either being a Democrat or a Republican, with the result that each of those parties needs all of the people on their side of the dividing line, no matter how ridiculously awful they are. Given a voting system which either allowed people to rank candidates, or gave results proportionate to the people who voted for them (or both)*, you wouldn't end up with your "I believe in capitalism but I'm not actually Satan" right-wingers feeling they have to support Trump, or with Hilary and Bernie supporters both telling each other that they have to support their candidate or the bad guys win. Instead you'd have actual separate parties - which would then, admittedly, have to work together to pass bills - but that's much easier when you have mixes of parties who aren't all so incredibly opposed to each other.
Basically, any system where splitting the vote means you lose is a terrible, awful thing which causes terrible politics. Like what we're seeing in the USA at the moment (and what we see whenever there's a UK-wide election).
And yet, while I see a lot of people in the UK talking about electoral reform, I don't see anything similar coming from the USA. I wonder why that is.
*Obviously for the presidential election you want to rank candidates, because there's only one person elected at the end of it, and you can't make just their left-foot Libertarian. Although that is an excellent idea for a short story that someone else should write.
Original post on Dreamwidth - there are comments there.