If we want to talk about Germany 1920-1945, the precedent for that to happen is Barack Obama and his executive branch overreach. Deploying the DOJ, the IRS, the EPA and others to become political puppets for his agenda. Promoting judicial members that believe the Constitution is an "ever changing" document open to VAST interpretation for the "times".
Only through these actions would a Third Reich German political system ever arise in the United States. Only if the checks and balances of the branches of government continue to degrade like they have over the last 8 years under Barack Obama.
Don't blame Trump or any future Republican President for forcing a more conservative (you might call it fascist but others might not) United States are your precious socialist views. Blame Obama for the precedent he set to allow it to happen in the first place.