And to add insult to injury it's for a caucus, a tiered delegate election type designed specifically for the constraints of the 19th century.
Actually, it's even older. Party conventions are what are from the 1830s. They replaced the congressional and local party caucuses which was considered not democratic enough.
States didn't use caucuses to determine delegates to the conventions but a whole variety of different methods. In fact, delegates to the Constitutional Conventions were more often than not
elected by the people. Even those sent to the Confederation Congress were often elected through methods that looked more like a primary-general or a run-off system.
Even in the presidential system, primaries date back to 1911. Caucuses replaced them as part of the Democratic Party's process. The Republican Party traditionally has just copied whatever the Democrats do because then the states will pay for it.