Former President Barack Obama on Friday mocked Herschel Walker, the GOP nominee for a U.S. Senate seat in Georgia, with a “thought experiment” that highlighted the Republican candidate’s lack of experience for the political role.

At a campaign rally for Walker’s Democratic rival Sen. Raphael Warnock (D-Ga.), Obama acknowledged that Walker was “a heck of a football player” and “amazing, one of the best running backs of all time.”

But that didn’t make him the best person to represent the state, the ex-POTUS argued.

Obama imagined people seeing Walker in the airport or hospital, and allowing him because of his success on the football pitch to fly the airplane or do surgery.

“You wouldn’t say that,” said Obama.

Obama said “the opposite is true too” in that people may have liked him as a president but they wouldn’t want his “slow, old, skinny behind” on the football field.

“You’d have to scrape me off the field,” he cracked, before flipping his “Yes we can” slogan to: “No, I can’t. No, I can’t.”

Watch the video here:

Elsewhere in Obama’s stumping for Warnock, he slammed Walker as “a celebrity that wants to be a politician” and attacked his “issues of character,” an apparent reference to allegations that Walker in the past paid for two women to terminate their pregnancies. Walker denies the claims. He is running on a strict anti-abortion agenda.

Walker would be so loyal to Trump it would mean “he is not going to be really thinking about you or your needs,” Obama added.

This article originally appeared on HuffPost and has been updated.

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