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LinkedIn founder and Silicon Valley billionaire Reid Hoffman is offering to donate up to $5 million to charity if Donald Trump releases his income tax returns.

Hoffman made his offer Monday in a post on Medium calling attention to a veteran's crowdfunding effort challenging Trump to release his returns. If the Republican nominee releases his returns before the final presidential debate on October 19, the CrowdPac effort launched by Marine Corp veteran Pete Kiernan will donate the money raised to a handful of veterans groups.

Despite numerous calls to publicly disclose his tax returns, Trump has refused, saying he would only release them once the IRS finishes an audit. Mike Pence, Trump's running mate, has already released his tax documents, as have Democratic nominee Hillary Clinton, and her running mate, Sen. Tim Kaine of Virginia.

Hoffman said if Kiernan's campaign reaches or exceeds its funding target, he will contribute to the campaign with a donation equal to quintuple (five times) the total raised, up to $5 million. Thanks to Hoffman's attention, the campaign surpassed its initial target in a few hours Monday.

"Given Trump's vocal support of veterans, I imagine he will recognize the great good that can come from Kiernan's proposal," Hoffman offered in his post.

As of this writing, the campaign had raised $50,000 toward a revised goal of $1 million.

Representatives for Trump's presidential campaign did not respond to a request for comment.