The problem with that version is that, just as in the national election, the candidates will only really campaign in the purple states with a lot of independent or undecided voters. I’d like to see them have to reach out to a diversity of voters within their own parties first. I’m not saying it’s more fair necessarily, just that I think it would be good for the process and maybe help each party wind up with a better (or at least more representative of the party as a whole) candidate in the general.