If you’re seeking the nomination of a major party, you have to go through the process of getting enough delegates to the party’s national convention to win the nomination. This explains that process:If you’re not running as a Democrat or Republican, you’ll need to get on the ballot in the various states. Each state has its own rules for getting on the ballot — in a few states, all you have to do is have a slate of presidential electors. In others, you need to collect hundreds or thousands of signatures of registered voters.