With the establishment of the national party convention, the process used to select the delegates to the national convention became of paramount importance. State and local party conventions selected the national convention delegates, but those conventions were often conducted in deeply undemocratic ways, excluding many party voters or using parliamentary rules such as winner-take-all and/or the unit rule to marginalize political minorities in the state. Nevertheless, the Democratic Party expressly endorsed the use of winner-take-all and unit-rule voting in the nomination process, which allowed party bosses to control the composition (and therefore candidate preference) of their state delegation. The Republicans were initially more hostile to boss control, forbidding the unit rule, but they, too, ultimately endorsed winner-take-all delegate selections in 1916. Moreover, both parties routinely seated delegates from states in which the convention process had been run in an undemocratic fashion. Thus, for most of the nineteenth and twentieth centuries, the party convention process was run by a small coterie of party bosses, who ultimately chose the party’s nominee.

Towards the end of the nineteenth century, frustration with party boss control of the nomination process continued to grow. At the beginning of the twentieth century, at the behest of Progressives, several states adopted the presidential primary election, allowing voters to directly participate in the nomination process for the first time. Both national parties accepted the validity of the primary election process, but the early primaries did little to empower ordinary voters. In most primary states, voters did not directly vote for the presidential candidate but rather for the individual delegates to the national convention, whose candidate preference was often unknown and not disclosed on the ballot. As a result, uncommitted and favorite-son delegations, both of which were typically stand-ins for the state and local party bosses, often won the primary elections. Moreover, even when a candidate won a state’s primary, the national convention often allowed delegates from that state to vote for a different candidate; the primary result was not viewed as binding. Thus, despite the initial promise of primary elections, ordinary voters remained on the periphery of the nomination choice.