Dictatorships usually come about through a military coup (or at least with the support of the military) or following a victory in a civil war. There is almost always an element of force.
But not always. Hitler, for example, came to power following a democratic election. He then installed a whole apparatus of terror and repression, but the real source of his power was the sense that he could not be resisted, and that everyone would do what they were told, since it was too dangerous to do otherwise.
Are we witnessing a similar scenario unfolding before our eyes in the United States? There we have a leader elected according to the US constitution, but acting increasingly as though he is subject to none of the usual constraints on the arbitrary use of power.
Donald Trump took office as President of the United States with an alarming ignorance of the country he leads and its history - and that included what seems to be a complete misunderstanding of how government works in a democracy and of the US President's role in that government.
His experience as a business tycoon and as a reality TV star seems to have persuaded him that being President means you can do what you like - without regard to any other elements of a democratic government.
So, when the courts declared his ban on certain entrants to be illegal, he was outraged - just as he is when held to account by the media. His response to the media is to lambast them for publishing "fake news". And then, when he had problems getting his healthcare legislation through Congress, he threatened that he would "close down" government.
He seems to think that the US courts, the country's legislature and the media are of no account, and that it is the executive alone - in the person of the President - that should exercise unbridled power.