Every four years, AFAIK, there are a dozen or more fringe candidates running. It would be insane to protect people no one even knows is running. Only thing it would accomplish is less security for people actually in grave danger.
There were, as I remember, 204 candidates.
Many Socialist, Labor, and Communist parties. Several Christian parties. A Falange Party. Something called the United Fascist Union. Black and white nationalist parties. An Objectivist Party. Parties with Liberty or Liberal or Conservative in the name. Also, several intentionally silly names, such as the Birthday Party. And some personal parties, such as the Vote For Fred Party.