So rather than voting all at once some individual states vote at different times and some vote together but rather than a direct vote their are 'caucuses' and rather than first past the post the delegates are awarded proportionally but if no one has a clear majority (which looks increasingly likely) they have a 'brokered' convention where the party can choose a candidate who didn't even campaign (Hilary?) and if they fail to do that the delegates can then choose any candidate they like without paying attention to the voters and superdelegates come into play who are essentially the party grandees who were never elected in the first place? I have to say, I think the Commonwealth system is so much simpler.
