POLITICAL parties are mentioned nowhere in the Constitution, and the party nominating process offers few of the protections associated with the ideal of “one man one vote.” Voters in early states have far more influence than voters in later ones. Votes in hard-to-attend caucuses effectively count more than votes in high-turnout primaries. Some primaries are open to party loyalists; others to all comers. The rules that assign convention delegates are byzantine, the delegate selection process is various, and a few states rely on conventions and cut the voters out entirely.
As Donald Trump attempts to clamber to the Republican nomination over a still-divided opposition, there will be a lot of talk about how all these rules and quirks and complexities are just a way for insiders to steal the nomination away from him, in a kind of establishment coup against his otherwise inevitable victory.