1968 Democratic Party presidential primaries
From March to July 1968, Democratic Party voters elected delegates to the 1968 Democratic National Convention for the purpose of selecting the party's nominee for president in the upcoming election. Delegates, and the nominee they were to support at the convention, were selected through a series of primary elections, caucuses, and state party conventions.
Source: Wikipedia — 1968 Democratic Party presidential primaries (CC BY-SA 4.0)