When presidential nomination contests are not wrapped up quickly in the first few weeks of voting, the slower pace of the primary calendar thereafter produces fertile ground for widespread gripes about the nomination process itself. The daily thrills and plot twists of February and March give way to the more tedious week-to-week slog of April and May, leaving more time and energy for broader evaluations of the nomination system. Supporters of candidates who are still actively campaigning but face diminishing odds of success can easily direct their frustration toward the rules and norms that seem to be responsible for preventing their desired outcome, even as backers of the front-runner express annoyance that their own favorite is still forced to withstand fire from also-rans within the party.
This year, the various procedural quirks of the process have received more than the usual amount of scrutiny—perhaps because both parties' races are still nominally unresolved as of late April (for the first time since 1980), because the insurgent Trump and Sanders candidacies are particularly sensitive to any apparent evidence that the deck has been stacked against them by the dreaded party "establishment," and/or because the internet has a way of amplifying dissatisfaction of every sort.
Everyone, it seems, has a list of grievances. The Trump campaign is suspicious that delegates are being unjustly denied them by state party conventions in Colorado and elsewhere. Anti-Trump Republicans lament delegate allocation rules that have disproportionately favored Trump and prevented non-Trump sentiment from coalescing behind a single rival candidate. Bernie Sanders supporters decry the existence of closed primary rules in some states; Hillary Clinton supporters decry the existence of caucuses in others. Behind many of these complaints is the assumption that one or both national parties wish things to be as they now are, presumably for some nefarious reason or reasons, and not only allow but encourage various infringements on democratic principles in order to serve other, less high-minded purposes.
Other political scientists have defended the parties and their role in structuring the nomination process. I wish to make a slightly different point, which is that the national party committees, though nominally in control of presidential nominations, face significant practical constraints in imposing their will upon the state parties and state governments that actually operate elections. Many of the specific aspects of the process that provoke popular disdain—the disproportionate influence of Iowa and New Hampshire, the inconsistency in delegate allocation formulas and voter eligibility requirements from state to state, the inept organization of many state caucuses—are, in truth, merely tolerated by the national parties. It is the states that insist upon them, and the states that therefore bear most of the responsibility for these departures from "pure" democratic equality.
Of course, the national parties could in theory attempt to impose stringent requirements on the states to smooth out these various inconsistencies, but practical complications are likely to ensue. If a national party were to mandate that all delegates be selected via primary elections, for example, but some states refused to authorize the public funds to hold them, what then? Would those states go wholly unrepresented at the national conventions—and, if so, would this be a more "democratic" outcome than the current system, which allows voters to attend party caucuses instead? Could the national parties insist on closed primaries nationwide, even though about half of American states do not have official party registration? Could they likewise require open primaries, even though some presidential primaries are held concurrently with primaries for down-ballot offices that might be influenced by the participation of voters from outside the party?
The imposition of strict national rules on the states and state parties is further impeded by the fact that the national parties, like the national government, are federal systems. National committees are comprised of representatives from the state parties, who select the national party chair and vote on internal party rules. A promise to crack down on the freedom of the states to run their primaries and caucuses as they prefer is unlikely to be a popular sentiment within any internal party committee or a winning platform for any candidate for national party chair. If anything, the state parties would prefer even more autonomy. Howard Dean ran successfully for chairman of the Democratic National Committee after the 2004 election by promising to direct more party money and resources to the state Democratic organizations, which turned out to be a very popular position among the ranks of the state party chairs who held seats on the national committee.
It is easy to look at the current complex and disjointed nomination system and call for large-scale reforms. Indeed, some reforms would be undoubtedly well-advised. But let's remember that others have come before us, with similar plans for changes to the process in the name of equality and fairness—and that their ambitions were foiled by the enduring ability of the states to defend their own turf against the attempted interference of the national parties. If you're looking to cast blame for what you don't like about the current nomination system, don't forget that the states deserve their fair share.