Ultimately the primary campaigns, at least for the main parties, are national campaigns. As a result of more frequent and more intensive media coverage- even during early primaries- candidates have to speak to national issues. Furthermore, Super Tuesday is basically a national primary already, it just happens to exclude some of the states.  The early primaries simply work to filter out candidates attempting to use the presidential election to promote a single, poorly developed set of maverick views in front of a much larger audience than they would otherwise have access to.  Only in the event of very close races are the later states left with any meaningful decisions. It would be far more useful to admit that reality and simply hold all national primaries in early February. Contests would still be organised by the state parties (in conjunction with the state authorities where required) and states would still record their vote separately.