The Puerto Rican Independence Movement ran several candidates but none of them won. They ran legally. There was a similar movement in Alaska.
Advocating for independence is not illegal but threatening to overthrow the Federal Government is.
The secessionist movement is not about overthrowing and taking control of the federal guvmint. Let them keep their tinhorn dictatorships.
The movement is about seceding, not overtaking. Separation. They keep what they think they have, we keep what we think we have. It is doable.