Donald Trump long thought he was going to be president. And we have proof.

The New York real estate mogul, who penned the book Trump: The Art of the Deal, signed a copy “Future President” over three decades ago.

In the book, President Trump signed, "Donald Trump Future President."

It happened the year he published the book, 1987, 32 years ago, at a book signing in Trump’s new Trump Castle casino in Atlantic City. The book buyer requested that Trump sign “future president,” and Trump didn’t resist.

Now it is going up for auction and could bring a sky-high $1,200 when it goes live at Alexander Historical Auctions on Nov. 21. It is one of several notable and newsworthy historical items our friends at Alexander are offering in their three-day online sale that beings Nov. 19.

Trump had long talked about running for president but only made moves to jump in during the last 10 years.

Here is how Alexander’s President Bill Panagopulos wrote up the book, auction item No. 1,376:

Donald Trump

(b. 1946) Controversial American financier, deal maker, and gambling mogul, once near bankruptcy, he recovered his wealth and successfully ran for president in 2016. Signed and inscribed book, Trump: The Art of the Deal, by Donald Trump with Tony Schwartz (New York: Random House), 1987, First Edition, 246pp. 8vo., his memoir and compendium of business advice. Trump signs on the front flyleaf in blue ink, adding a prescient inscription: "Future President". In very good to fine condition. The book is accompanied by a typed letter of provenance from the original recipient, in which he describes purchasing the book at a signing event at the Trump's Castle casino shortly after its release in November of 1987, and his request to Trump that he sign it as "Future President.”