Jeb Bush himself had been an adviser to Lehman Brothers investment bank. | Getty

Former AIG chairman Hank Greenberg invests $10 million in Jeb Bush

01/07/16 07:42 AM EST

Updated 01/07/16 12:06 PM EST

Billionaire Republican donor Maurice “Hank” Greenberg has donated $10 million to the super PAC backing Jeb Bush’s presidential campaign, according to The Wall Street Journal.

The Journal on Thursday reported the former American International Group CEO’s contribution, which he didn’t deny in an interview with the newspaper, though he declined to discuss it. In an October interview with Bloomberg Politics, Greenberg said he was supporting Bush and would donate to his super PAC.

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Greenberg headed AIG from 1968 until he was pressured to step down in 2005. During the 2008 financial crisis, the Federal Reserve rescued the multinational insurance company with a bailout that grew to nearly $185 billion after it became virtually insolvent, and the government took control of roughly 80 percent of the company. To much public ridicule, Greenberg filed a class-action lawsuit against the federal government in 2011, arguing that the Federal Reserve had overstepped its legal authority during the bailout. He won the case in June but was awarded none of the $40 billion he sought in damages.

Bush himself was an adviser to Lehman Brothers investment bank, which collapsed during the 2008 financial crisis. According to tax records the former Florida governor released earlier in his campaign, Lehman paid him upwards of $1 million a year after he left office in 2007. Bush’s tax filings also show that Barclays, the bank that bought Lehman Brothers out of bankruptcy, later paid Bush $2 million a year as an adviser through 2014 as he considered mounting his White House campaign.

Kentucky Sen. Rand Paul blasted Greenberg’s contribution. “Former head of AIG gives $10 million into Bush super Pac,” Paul tweeted. “Bush super Pac is using his brother’s bailout money to bail out his campaign.”

Greenberg has previous links to Bush, having supported Florida’s natural-disaster relief effort during Bush’s second term as governor. After a series of hurricanes blew through the state, including Hurricane Charley in 2004, Greenberg — then the chairman of an AIG-affiliated foundation — donated $1 million.

The $10 million donation makes Greenberg one of the largest known megadonors this cycle and further bolsters the Right to Rise super PAC supporting Bush’s campaign. The record-setting super PAC exceeded its $100 million fundraising goal last summer and has spent more than $47 million in advertising, far outspending the rest of the 2016 field.

But as Donald Trump, who has eschewed any super PACs supporting his bid, continues to dominate nationally and in early-voting states such as New Hampshire, it’s unclear how effective TV advertising will be in this election. Trump only this week began airing his own ad, a 30-second spot running in Iowa and New Hampshire.