So while the US is by far primarily comprised of two main political parties, those parties are private organizations.
That being said, soon both candidates will be officially briefed by the US government with highly classified information to prepare them for the presidency. Since there hasn't been a government run election yet, only private elections for party nominations, how does the government decide which candidates are "worthy" of receiving this briefing?
Specifically, what is the policy for the US government to decide that the Democratic and Republican Nominees can be briefed with classified information, but candidates elected as nominees of smaller minority parties cannot?
Do they just look at private polls, the media, and "wing it"? It's common sense that they're the only two who have a chance to win but processes involving sharing national secrets with people including senators, governors, and reality TV show stars seems like they would have some form of strict policy to determine how much of a following the candidate needs to receive the briefing in case of a "third party" candidate becoming popular, including a specific method of measuring each candidate's following.