Donald Trump and Hillary Clinton shake hands at the first presidential debate, at Hofstra University. (Andrew Harrer/Bloomberg News)

I think this may be my fault.

Where I come from, none of this has happened. President Jeb Bush sent me back in time to kill Baby Hitler, and I am afraid that I have made a terrible mistake.

Where I come from, the election of 2016 was something of a foregone conclusion.

All the headlines in my timeline have been about the deja vu of it all. If I have seen one joke about another Bush-Clinton election, I have seen 90. Nobody was all that jazzed about Jeb, and Ted Cruz (of all people) gave him a run for his money, but in the end he proved that if you throw enough money at people, they will decide you are interesting and deserve their support.

Samantha Bee has taken over “The Daily Show,” but everyone still misses Jon Stewart.

There are moments, still, when I see flashes of my old timeline. Jeb Bush appeared at the Emmys, for some reason, in a sketch that made total sense when it had Donald Trump in it.

In my timeline Seth Meyers was very nice to Donald Trump when he sat in the audience at the White House correspondents’ dinner (how could he not have been nice to our Donald Trump?) and he did not run for president. He had nothing to prove to anyone.

But our Donald Trump is a very different man.

It is amazing how tiny changes to the timeline can reverberate. I thought I was careful. I never strayed from the path. I accidentally crushed one butterfly, but all of us time travelers are forced by law to carry butterfly revival kits because of an incident that nearly happened one time.

But it’s the butterflies you don’t step on.

There was one butterfly in 1920 that a time traveler needed to crush or there would be enormous consequences, and I missed it. It flew off.

The butterfly did not create extinctions. Our orthography is still much like yours. But one of its descendants distracted Mrs. E.B. Hamilton at a stoplight with its gossamer wings and, as a consequence, she did not get home in time to start her novel. She was supposed to write “The Kingfisher.” Instead she cooked dinner, watched television, played with her two daughters and went to bed. And then every day something different happened, and she never found the time, had a full, pleasant life, but always with an unwritten book rolling like a loose marble in the back of her mind.

In our timeline “The Kingfisher” is Donald Trump’s favorite book.

He read it very nearly by accident. A new nanny in the Trump household did not know what the house rules were and forced him to sit quietly and read a book, just one book, so that she could make a phone call. When she got back he was still reading.

He loved it. He had never thought of anything like it. He spent his weekends sitting seasick in the back of a limo, reading as they drove to visit his father’s tenants. A whole new world opened up to him. The cover fell off and he bought another copy.

When he got to Wharton he still was carrying it, because it soothed him to reread the long section set in the ice cave, and after his first class a young woman with enormous glasses came up to him and said “Hello, I don’t remember what your name was, but I could not help noticing that you were reading ‘The Kingfisher.’ It is my absolute favorite book.”

“Mine, too,” Donald said.

This was their beginning. He carried her books out of the classroom and they spent hours just talking, excited and relieved to find another human being who looked at the world and saw the same things. She recommended more books to him. He read them. The world became like an inside joke to the two of them. After a few months he started to be irritated with himself for not noticing that she was beautiful.

In my timeline they are still married.

Our Donald Trump does not have a Twitter account. He never met Roy Cohn. He did not fuel the birther movement. Nobody who had read and understood “The Kingfisher” could have. He bought a full-page newspaper ad about the Central Park Five but what it said was the opposite.

His name is still on buildings but at least one of those buildings is a library.

He still lives in Manhattan in an expensive and ugly apartment, but it is to his taste, and there are books everywhere — on the floor, on the expensive carpet, in the bathroom. Not everyone loves him but he does not need everyone to love him. He has people who really know him. He has real friends — male and female — people who send him little clips from YouTube that they know will amuse him, and he does not sit amidst crowds feeling completely alone.

He reads every day.

In my timeline the Republican Party still needs to reckon with the coalition it has created — just, not yet.

I don’t know if I will be able to repair this and return to my timeline. Perhaps by the time you read this I will already be gone. I am going to find Hillary Clinton, the one person who is always doing exactly the same thing in every timeline, even the one where everyone is an enormous bearmonster with long pendulous tentacles, and ask her.

But either way, I pity you. If you are reading this, you have to live in this one.

(I got Baby Hitler, by the way, but the second I turned around another time traveler had already come along and put him back.)