There are rules, you see. Many, many rules. So speaketh the DNC.
In order to get a spot in the first two televised national Democratic debates, you must reach at least one of two goals. 1) Get 65,000 unique donors to your campaign; or 2) score at least 1% or more in three separate polls in a nationwide or Iowa, New Hampshire, Nevada, or South Carolina poll from a predetermined slate of poll takers.
And, there can only be 20 total candidates (that's another rule).