Ever wonder why Donald Trump looked so at ease during his speech at the Republican National Convention last month? It could have been a strange case of "practice makes perfect."

More than a decade before his on-stage appearances in Cleveland, the GOP presidential nominee approached the podium to endorse another well-known American whose words are frequently controversial: Eminem.

At a New York City launch party for Slim Shady's satellite radio station Shade 45 in 2004, Trump took the stage to raucous applause from the crowd at the "Shady National Convention" in a case of life imitating art.

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"I'm Donald Trump, I'm always right," he told the gathering of fans.

"I know a winner when I see one, and Donald Trump is telling you right now that Slim Shady is a winner! He's got brains, he's got guts, and he's got Donald Trump's vote!"

Who knew that 15 years later he would end up running for president?

Watch the full video below, or click here.