Like a feisty little terrier scampering after the wheels of a big, fast-moving SUV, Mark Cuban has been nipping at Donald Trump’s heels for more than a decade. The Dallas businessman’s latest effort to bite The Donald: offering $10 million to charity if the GOP presidential nominee would sit down for a four-hour interview with Cuban about policy issues. (Come on—only four hours?) The Dallas Mavericks owner also predicted the U.S. financial markets would “tank” if Trump ever made it to the White House.

Cuban hasn’t always been so antagonistic to his fellow billionaire, though. (Forbes says Trump’s net worth is $4.5 billion; Cuban’s, $3.2 billion.) Not much more than a year ago, in fact, Mark was practically begging to be Trump’s vice presidential pick. Even as recently as May and June, he said he was “open” to being The Donald’s—and Hillary Clinton’s—VP. So, what changed? Cuban claims he learned that Trump isn’t interested enough in learning about world affairs to merit his support. But, given Cuban’s history with the New York businessman, that doesn’t really pass the smell test.

In fact, Cuban’s been taking little potshots at the better-known billionaire for years. Cuban says it all started in 1999, when he visited Trump’s Mar-a-Lago resort for a Super Bowl party and, Cuban claims, Trump talked down to him. But the real public feud kicked off after Cuban’s ABC-TV show The Benefactor — widely considered a pale imitation of Trump’s top-rated The Apprentice — sank like a rock in 2004.

Trump wrote in a book that The Benefactor tanked so quickly because Cuban “has absolutely zero television persona or personality.” In addition, he continued, the Dallas billionaire has “the look of a Neanderthal,” and “just doesn’t get it.” Cuban fired back, trash-talking Trump to a newspaper reporter: “In the [Apprentice] boardroom, he doesn’t know what he’s doing. The lessons he gives on The Apprentice are garbage. I’ll put up the lessons from The Benefactor against his any day.”

By 2006, when Trump came to Dallas to speak at a “wealth expo” for the Learning Annex, his attitude toward Cuban had softened. “I saw Mark the other night, when the [Mavs were playing the New York Knicks], and I think he’s a terrific guy,” Trump told me during an interview for the Dallas Business Journal. “Honestly, Dallas is lucky to have him. He works so hard at creating and giving a good team to Dallas. … I think he’s a great character, and I think he’s been great for Dallas, great for the team. And you’re probably shocked to hear me say this.”

Fast-forward to five years later, and the feud cranked up again when Cuban said he’d give $1 million to Trump’s favorite charity if The Donald would shave off his trademark hair. Replied Trump on Twitter: “Dummy [Mark Cuban] is at it again trying to use me to get publicity for himself!” Then he added: Cuban “tries so hard to be a star and he truly doesn’t have what it takes and never will!”

The next year Cuban goaded Trump once again, this time challenging him to donate $1 million for relief efforts following Superstorm Sandy. Their Twitter tiff raged on, of course, with Cuban responding to a Trump tweet this way: “You got me DJT. I’m intimidated and at a loss for words. What a zinger. I’m done for. Dayuummm. SMH. ITTBYCD? ILTS!”

Two months ago, Cuban officially endorsed Clinton at a rally in his native Pittsburgh, where he proceeded to call Trump a “jagoff.” Then he added: “Is there any bigger jagoff in the world than Donald Trump?” Gee, I dunno, Mark. But if you give me a minute, I could probably think of one.