or primaries

a spoiler effect happens when a losing candidate affects the results of an election simply by participating

Vote splitting is the most common cause of spoiler effects in FPP. In these systems, the presence of many ideologically-similar candidates causes their vote total to be split between them, placing these candidates at a disadvantage. This is most visible in elections where a minor candidate draws votes away from a major candidate with similar politics, thereby causing a strong opponent of both to win.

That the US voting system lacks the sincere favorite criterion is mathematical fact: lesser-evil voting is necessary to avoid losing the best chance of getting anyone preferable to the worst major candidate. Denying that is like denying laws of physics. You can’t coerce logic & causality to your will. Just because you don’t understand that doesn’t mean others don’t. Primaries exist to select better major party candidates.

Viable 3rd party candidates requires voting reform, which again requires passing those reforms through the current system.