Maserati wrote:
Went to polling station this morning, the guy who runs the whole show is a friend. He said that turnout is crap, but about as he expected. My wife said that everyone is still on the ballot—Klobuchar, even Booker. I don’t profess to understand how it works.
You have to pay by a certain deadline to get your name on the ballot, usually months in advance. Any serious candidate with even a mildly funded campaign would make sure they're on the ballot at least up till Super Tuesday.