I used to propose at this address a framework for multistage single-winner elections for the US. I am no longer comfortable with the proposal I had up, so I have withdrawn it.
I still hold that it is very important to defeat the vote-splitting effect. If the US can have proportional representation, that would probably be good, but that can only work for legislatures. For any single-winner offices that the citizens of the US allow to continue in existence (e. g., governors and president), I recommend Range Voting also known as Score Voting. A simple version of Range Voting is Approval Voting.