I wouldn't use such a broad brush for painting.
The way that the "nominating process" works in the US political system is that ANYONE is allowed to "declare" that they are a "candidate" for ANY political party (even if they have absolutely no idea what that political party's platform is [or even if there is such a political party]) AND, if NO OTHER "candidate" also "declares" that they are a candidate for that political party then the sole person who "declares" that they are a "candidate" for that political party gets their name put on the ballot as the OFFICIAL candidate for that political party.
To take it to an absolutely ridiculous extreme, if Adolf Hitler (assuming he is still alive) were to "declare" as a "candidate" for the Democrats - and no one else did - and if Josef Stalin (assuming he was still alive) were to "declare" as a "candidate" for the Republicans - and no one else did - in the same electoral district AND IF the only other "candidate" was from the "Militant Vegetarian, Pro-Homosexuality, Protest Party" then the voters would have to chose between
- [*someone with a "Big D" after their name;
- someone with a "Big R" after their name; and
- someone with a "Big MVPHPP" after their name.
I rather suspect that voter turnout would be rather low.