In 1970, after the tumultuous Democratic convention of 1968, the Democratic Party issued a "Mandate for Reform," allowing "the people" (instead of the party bosses) to choose their candidate. The result has been a system of “primaries,” subsequently modified by Democratic "superdelegates," but  still the prevailing process among the Republicans.
In contrast, the Constitution mandates selection of the president by an Electoral College, expected to be wiser than, and above the passions and self-interest of, the common folk. It is rather strange, then, that we are entrusting the selection of these party nominees to the very same common folk whom our Founding Fathers considered ill-prepared to vote in the general election!
So how have those folks done so far?