Oklahoma oil billionaire Harold Hamm didn't wait long to make a nearly $1 million donation to a group supporting Republican presidential candidate Mitt Romney after he became one of Romney's top energy advisers in March. Just weeks after Hamm joined the Romney campaign, he gave $985,000 to a pro-Romney super PAC, according to campaign reports.

Hamm's company, Continental Resources Inc., oversees oilfield stakes in North Dakota and Montana, and Hamm has been disdainful of President Barack Obama's energy policies. On his personal website, Hamm complained that Obama and his administration "have done everything in their power to stop fossil fuel usage."

Hamm, whose company did not return telephone calls from The Associated Press, is among a group of energy tycoons who have made lucrative donations to Restore Our Future, a super PAC supporting Romney. Unlike the others, Hamm has matched his contributions with his role personally advising Romney on energy policy — blurring the line between the campaign and the super PACs that support them but are legally barred from coordinating with candidates.

"Given the idea that super PACs were supposed to be independent, it seems odd when you've got someone working for the campaign who turns around and gives large contributions to the independent group," said Lawrence Noble, a Washington attorney and former general counsel for the Federal Election Commission. "That's not what most people's idea of what independent is."

Such contributions are legal, said veteran elections and ethics lawyer Jan W. Baran.

"It may be an appearance problem, but it's not a legal problem," Baran said.

Romney's campaign said Hamm's contributions to the super PAC supporting Romney were unrelated to his policy advice.

The overlaps between super PACs and presidential campaigns take other forms as well. Former Obama and Romney officials play key roles in the operations of major super PACs. Bill Burton, a former Obama press official, co-founded the pro-Obama Priorities USA Action. Carl Forti, Romney's 2008 national political director, co-founded Restore Our Future.

Hamm, whose personal holdings are worth $11 billion, according to Forbes, was named chairman of the Romney campaign's Energy Policy Advisory Group on March 1. A promoter of the oil industry and a skeptic of Obama's emphasis on low-pollution "green" energy, Hamm is fiercely protective of his firm's majority stake in the Baaken formation, a 15,000-square-mile tract strewn with deep-rig wells and hydraulic fracturing sites, where natural gas and oil are extracted in a process also known as "fracking."

Hamm has complained about federal rules, permit delays and the refusal to build the Keystone XL pipeline to carry oil from Canada to refineries on the Texas Gulf Coast. "All of these actions are designed to result in higher costs at the pump for the consumer," he said. He also criticized what he said were billions of dollars in subsidies being given to solar, wind and other alternative sources of energy.

Continental has repeatedly objected to proposed Environmental Protection Agency rules for oil and gas fields in North Dakota and Montana. Last April, the EPA gave oil and gas producers in those states until 2015 to comply with toughened anti-pollution standards.

Hamm also complained about a federal misdemeanor prosecution last year that targeted his firm and several other energy companies in the deaths of 28 migratory birds found near oil fields — a case dismissed by a federal judge.

"Producers need regulatory stability, not threats and lawsuits by the Department of Justice nor increased regulations from all governmental agencies," Hamm wrote on his CEO Insights blog just weeks before he gave $985,000 to Restore Our Future.

Other oil executives also support Romney's campaign. William Koch, who heads the Oxbow Corp. energy conglomerate, has given at least $2 million to the super PAC, either personally or through corporate subsidiaries. Joseph Craft, whose Alliance Holdings is a major coal producer, gave $500,000. There are smaller but sizable donations from other coal and oil producers.

On his campaign website, Romney advocates for more pipelines and opening U.S. oil and gas reserves for more development, and he opposes what he describes as over-regulation of shale gas stakes. Romney's campaign also warned that "we should not be in the business of steering investment toward particular politically favored approaches."