They do not prevent it.They only make it more difficult. What will prevent it is a strong civilian population well armed and schooled in the advantages of freedom and capitalistic enterprise. Or Apres Trump le deluge.
Apres Trump c’est certainment le Deluge. The Democrats are not going to allow it to be screwed up again. They will manufacture enough votes to take the whole ball of wax and there will be no more change of party in power. How that works out on the street is open to question but the Republic and its Constitution will be over. It cannot be restored once definitively gone.