The Democratic primary process is a lot more complicated than the Republican one, for reasons that only sort of make sense. Candidates used to be chosen in those legendary "smoke-filled rooms" with party heavyweights. Over time, the process became more democratic (with a small d) and part of it was organized to give weight to people who didn't usually get a voice. That's why they started to stagger the primaries and include the caucus system. They figured with a mix of different kinds of competition they'd end up with the best candidate. There's a case to be made for cleaning up the system and converting it to a totally national primary, but the fear there is that the candidate with the most money will win.