It's hard to find a precedent for the petrol the GOP is pouring on the US political system. The nearest might be the Conservative Party pre-1914, which armed paramilitaries and talked of "breaking the parliamentary machine". I wrote about this here [1/3]: https://www.newstatesman.com/politics/uk/2019/09/breaking-parliamentary-machine-lessons-1914-crisis

2. This is not an encouraging precedent. The Conservative Election Guide in 1914 told voters that "'Britain may soon be stained by the blood of civil war. No method remains, except armed revolt, by which the country can make its will prevail". Posters looked like this:

3. Probably only the outbreak of the First World War prevented serious civil conflict in Britain. Once a major party begins telling voters that elections have been stolen, that laws should not be obeyed and that resistance is a patriotic duty, it's very hard to roll that back.