How's this for a 2016 scenario?

Trump doesn't get the Republican candidacy, so he decides to run as an independent.

Sanders doesn't get the Democratic candidacy, so he also decides to run as an independent.

We could have a four-way race, Bush versus Clinton versus Trump versus Sanders. Where oh where are coalition governments when you need one???

Oops, Bush is cutting staff by 40% in a money-saving move. He's toast.

Cue Rubio.

I think the four-way race you describe would undoubtedly throw the election into the House. And we can only imagine what horrors they may inflict on us.