Voting and protesting have been attempted for decades, at least. They also are not enough. Those who wish to save the Union should look more closely at "etc".

Depends on the protests. E.g. the French beheading their king was also a protest.

Eh, not really. If he had been killed by a random brick thrown by a random protester, we could credit that to "protest". Louis XVI was arrested by the national army while attempting to flee the nation. After months of imprisonment by civil authorities, he was sentenced by a national assembly to be executed in the normal fashion for the time. That's really stretching the definition of "protest".