If two political parties are going to continue to dominate US politics, it means only two people have any real chance in the presidential election every four years: the Republican and the Democrat.

So while a lot of Americans express frustration with the system and say they’d like more options on Election Day, if a voter wants to help decide who those two candidates are, they’ve got to take part in the party primary system.

But the idea of regular voters participating in the primary process is relatively recent. New Hampshire didn’t put candidate names on primary ballots until 1948, and those ballots didn’t start affecting elections until 1952.

It used to be that presidential candidates were selected at party conventions. And it was mostly party members who selected delegates who went to the convention to vote.

Conventions still happen, but they’re mostly ceremonial since primaries have picked every candidate for more than 50 years. Violence broke out at the Democratic convention in 1968, the last time a party picked a candidate who hadn’t won any primaries.

That candidate, Hubert Humphrey, was shellacked on Election Day by Richard Nixon. That year was also the last election in which an independent candidate won any electoral votes in November — the segregationist Alabama Gov. George Wallace won five states in the South.

A lot has changed since then, but US politics hasn’t gotten any less confusing.

Every state conducts their own primary or caucus and none of them do it exactly the same way.