Rick Perry challenged Donald Trump to a pullup contest today in response to the billionaire's charge that Perry wasn't smart enough to join the presidential debate —- or as a reporter put it to Perry, not tough enough.

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"Let's get a pullup bar out there and see who can do the most pullups," Perry told a reporter, who told him that Trump "questioned your energy, toughness and quote-unquote, 'brain power' that it might require to run a successful campaign."

In a story on the Daily Mail, Trump said that Perry was "trying so hard."

"But it's not about trying," he said, according to the story. "It's about energy, it's about brainpower, it's about toughness."

Trump, who is competing for the Republican nomination and is polling well ahead of Perry nationally, tweeted earlier this month that Perry "should be forced to take an IQ test before being allowed to enter the GOP debate."

.@GovernorPerry failed on the border. He should be forced to take an IQ test before being allowed to enter the GOP debate. — Donald J. Trump (@realDonaldTrump) July 16, 2015

Trump's camp did not immediately respond to a request for comment.