Most everyone thought the idea of Trump actually becoming president was a huge joke.

Really— DONALD TRUMP as president of the United States? That’s a completely insane idea. Never gonna happen. Even Republicans wouldn’t stand for it.
-He’ll get his ass kicked in the primaries.
-The “Access Hollywood” video will destroy him.
-His insulting a Gold Star family and Senator McCain will cause an erosion of support.
-He’ll be buried by a Democratic landslide in 2016.
-He’ll be thrown out of office by 2017.
-The Stormy Daniels scandal will ruin him.
-Wait until the Russia collusion ALL comes out!
-Wait until the money-laundering documentation comes out!
-Robert Muller will torpedo him.

Clearly, American politics— and specifically the Republican Party— aren’t what they once were. Nothing should be considered off the table. They’d be ecstatic if any Trump— Donald, Junior, or, crazy as it sounds right now, Ivanka— could be a figurehead for American far-right nationalism.

From The Daily Beast, 11/24/18, on this unlikely but possible scenario—
What If Trump Actually Tries to Serve Three Terms?
by Matt Lewis
<snip>
The rise of Donald Trump—a president whose authoritarian tendencies are on full display—makes what might otherwise seem like a paranoid concern a little more plausible.
<snip>
[Regarding Trump’s repeated joking about a third term] This was shtick, but humor can be a safe way to launch a trial balloon—or to inject an idea into the public sphere. The fact that Trump’s audience laughed and applauded his comments is less than desirable.

One potential worry could be that a president could use some sort of national emergency—say a widespread terrorist attack—as a pretext for postponing elections. I’m not suggesting some sort of false-flag operation, but instead that a legitimate national emergency provides an opening. (This wouldn’t be entirely unprecedented. After the 9/11 attacks, then-New York City Mayor Rudy Giuliani tried to extend his term for three months.)
<snip>
But it’s wiser to overreact than to underreact. Liberal democracy is precious. Even if the odds are slim that the president would try to take a page from Putin and Xi—men, it seems, Trump admires—the stakes demand that we remain vigilant.
<snip>