The billionaire co-founder of LinkedIn, Reid Hoffman, has pledged to give up to $5 million to veterans groups if Donald J. Trump agrees to release his tax returns before the Oct. 19 presidential debate.
Mr. Hoffman announced his challenge in a statement published Monday on Medium that said he was offering a matching donation to support a crowdfunding campaign started by Peter Kiernan, a former Marine.
By midday Tuesday, Mr. Kiernan�s fund-raising on Crowdpac.com had raised more than $74,000 toward its $1 million goal of donating funds to 10 nonprofit organizations that help war veterans. Mr. Hoffman offered to match those donations 5 to 1 up to $5 million.
He said that offer was inspired by Mr. Trump�s own pledge in 2012 to donate that amount to a charity if President Obama revealed his college and passport records and applications. At the time, Mr. Trump had been questioning whether Mr. Obama was born in the United States (indeed he was, in Hawaii).
�Taking Trump�s own 2012 offer to President Obama into account, I�d like to assist Kiernan in his campaign,� Mr. Hoffman wrote.
�In a functioning democracy, the public shouldn�t be forced to bargain with a major presidential candidate to obtain access to his tax returns,� he wrote.
Mr. Trump�s failure to release his tax returns has drawn criticism not only from supporters of Hillary Clinton but from prominent Republicans, including Mitt Romney, who lost to Mr. Obama in 2012. On Friday, Mr. Trump�s running mate, Gov. Mike Pence of Indiana, released a decade of his own tax returns, but Mr. Trump and his campaign have said that the nominee would not release his until an Internal Revenue Service audit was completed.
Mrs. Clinton released a batch of returns last month. They showed that she and her husband, former President Bill Clinton, had an adjusted gross income of $10.6 million for 2015. They paid about $3.6 million in federal taxes for an effective tax rate of about 35 percent.
Candidates are not required to release their returns, but if Mr. Trump fails to do so before the election, he would be the first major-party presidential nominee in four decades to withhold them. This has fueled speculation that Mr. Trump�s returns would reveal facts about his wealth, charitable donations, business relationships or tax arrangements that might be politically damaging.
The returns might resolve questions about Mr. Trump�s own charitable giving. The Washington Post has reported that the candidate has exaggerated the amount he has donated to veterans groups over the years. An emailed request to the Trump campaign for comment about Mr. Hoffman�s pledge was not immediately returned on Tuesday.
In 2002, Mr. Hoffman, formerly the chief operating officer of PayPal, formed a small team to work on what would become LinkedIn, a professional networking site. It was introduced in 2003. This June, Microsoft said it would acquire LinkedIn for $26.2. billion.
After posting his pledge to Medium, Mr. Hoffman later updated it to disclose that he had at one time made an investment in Crowdpac.com. A Buzzfeed report and Shane Goldmacher, a Politico reporter, noted that Mr. Hoffman had promoted Crowdpac before by signing on to a campaign to recall the judge in the Stanford University rape case, Aaron Persky.
�The ingenuity of Kiernan�s proposal is how it gives Trump a strong incentive to act but doesn�t reward him directly for something he should have already done,� Mr. Hoffman wrote. �Instead, men and women to whom all Americans owe a great debt of gratitude will benefit from any positive action he takes.�
Mr. Hoffman�s announcement was reported on Monday night by news media including Forbes, which noted that Mr. Keirnan�s campaign had raised a meager $5,000 before the post.
�This is crazy, please help me get to this goal,� Mr. Kiernan said on his campaign page after the announcement.
A 26-year-old former Marine who served in Afghanistan in 2012, he wrote on Monday that the campaign was a way to take advantage of the �political climate� to raise money while also holding Mr. Trump accountable.
�The nation entrusts its defense to this small group of talented and determined patriots, in return for this responsibility the nation asks for honesty and integrity,� he wrote, addressing Mr. Trump. �I believe that to be the Commander-in-Chief of this group, you should be held to the same standards.�He noted that it would not cost Mr. Trump any money, just the release of his returns. He added: �So what do you say Mr. Trump, can you walk away from this deal?�