A pioneer of the leveraged buyout, Simmons and his holding company, Contran Corp, was the largest backer of Texas Governor Rick Perry's failed presidential bid.
Simmons himself gave $100,000 to Americans For Rick Perry, another affiliated group, but later gave $500,000 to Winning Our Future, a Super PAC supporting rival Newt Gingrich as Perry's campaign faded in the polls.
Contran's political action committee also gave $5,000 donations, the legal maximum, to Republican candidates Mitt Romney and Tim Pawlenty.
That approach is common in Texas, where donors commonly spread money around in order to ensure access.
Simmons has been one of Perry's biggest backers during his tenure as Texas governor, a time when his company Waste Control Specialists LLC sought to set up a lucrative nuclear waste dump in the sparsely populated western part of the state. Perry sought to sideline a state commissioner who opposed expanding the scope of the project.
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A company spokesman pointed to Simmons's extensive donations to Republicans as evidence that he was not targeting Perry for any special favors.
Simmons's donations were not limited to the political arena. He and his wife had pledged to give more than half of their wealth to charity, joining an effort launched by investor Warren Buffett.
Simmons had also pledged more than $177 million to health research efforts at the University of Texas-Southwestern in Dallas, and another $50 million to Parkland Health and Hospital System, a public hospital in Dallas.
His charitable foundation supports a wide array of causes, including some that might anger conservatives.
In 2010, the Harold Simmons Foundation gave $75,000 to public broadcasting organizations, $2,500 to Planned Parenthood, and $25,000 to Public Campaign, a Washington-based organization that "aims to dramatically reduce the role of big special interest money in American politics."