How Doonesbury predicted a Trump candidacy in 1999

Garry Trudeau has been drawing electoral commentary for nearly a half-century, as well as rendering Republican Party nominee Donald Trump for the majority of those years. Back in 1999 he produced this remarkably prescient strip:
In fact Trudeau first alerted the world to a possible Trump presidency nearly 30 years ago:
A recent book by the Pulitzer prize winner chronicles 30 years of Trump:
Mr. Trump isn't a fan: “Doonesbury is one of the most overrated strips out there. Mediocre at best.” --Donald Trump, 1989