The millionaires, billionaires and companies giving big sums to political committees supporting Mitt Romney, Newt Gingrich and Barack Obama have important business with the next president. Some are already in trouble with the government. Some are pressing for new laws or regulations that would benefit their interests in energy, mining and high finance.

The Associated Press reviewed financial reports, regulatory filings, court records, public statements and more to identify favors that the biggest donors so far in the presidential campaign might want in return for their contributions worth $100,000 or more. In some cases, these donors have given $1 million or more to help Obama's challengers or the president.

An exhaustive review of their motives is nearly impossible, since new federal rules governing such contributions allow donors to effectively remain anonymous if they funnel cash into the campaign through corporate partnerships or other mechanisms that can frustrate investigation.

The presidential campaigns all have said they do not trade political favors for election money.

Among AP's findings:

—An energy firm run by William Koch, a $1 million donor to the pro-Romney political committee, paid to lobby Congress on mining and safety issues and also over a proposed federal land swap that would enlarge the donor's Colorado ranch.

—The casino company run by Sheldon Adelson, the billionaire whose family has given $11 million to a political committee that supports Gingrich, has acknowledged it's under federal investigation by the Justice Department and a civil probe by the Securities and Exchange Commission for possible violations of the Foreign Corrupt Practices Act. The company denies wrongdoing and says the investigation stems from an allegation by a disgruntled employee. Adelson's family has provided nearly all the money that the pro-Gingrich group has received so far.

—A hedge fund run by a New York investor, Paul Singer, who gave the pro-Romney group $1 million, has pushed for federal laws that would give official U.S. backing to the firm's legal efforts to profit from the debt of distressed and Third World nations.

—A board member and former chairman of a prestigious Los Angeles hospital, John C. Law with the Cedars-Sinai Medical Center, has given the pro-Obama committee $100,000 as the hospital has lobbied Obama's administration over Medicare and Medicaid funding for teaching hospitals and electronic medical records, the National Institutes of Health and Army research programs.

— A Pennsylvania coal producer, Consol Energy Inc., which donated $150,000 to the pro-Romney group, paid a $5.5 million fine last year for violations of the Clean Water Act at six of its mines. It is lobbying to prohibit the federal government from regulating greenhouse gas emissions. Weeks after the company gave money to support Romney, who previously had agreed that humans are contributing to climate change, the candidate appeared to back off that position and said he would oppose spending high amounts of federal money to reduce carbon dioxide emissions, like those from coal plants.

The high-dollar contributions have flowed into the presidential campaign through so-called super PACs, which can support a specific candidate but can't lawfully coordinate their spending with a candidate's campaign. The groups, given a green light by the Supreme Court in 2010 when it stripped limits on corporate and labor union spending in elections, have already proved to be strategically successful for candidates. The pro-Romney group, Restore Our Future, spent $8.8 million on ads in Florida alone — more than Romney's own campaign — and has already booked TV spots in Arizona, Michigan and Minnesota.

A Romney campaign spokeswoman, Andrea Saul, dismissed any suggestion that wealthy donors are motivated by their private interests to fund the committee's operations.

"To the degree Americans support Mitt Romney," she said, "it's because he can reverse the decline of the Obama economy and get Americans back to work."

Obama so far has fewer big-money donors. He is able to marshal the resources of the Democratic National Committee, and it is typically easier for incumbents to raise money closer to the November election.

Public-interest groups have warned since the Supreme Court ruling that wealthy individuals, corporations, unions and other interests would seek favors in return for unlimited campaign contributions.

"The size of these donations counts for a lot, and the candidates will naturally be grateful to these organizations and their donors," said Sheila Krumholz, executive director of the nonpartisan Center for Responsive Politics in Washington. "And with greater support, comes increased gratefulness."

Consol, which gave $150,000 to support the pro-Romney group, is the largest producer of coal from underground mines, with operations in Pennsylvania and West Virginia. It also has interests in natural gas, using hydraulic fracturing — known as fracking — to extract gas with high-pressure streams of water, sand and chemicals.

Most of Consol's coal is sold to electric utilities. Such utilities are the dominant source of sulfur and carbon dioxide emissions, and Consol has backed Republican efforts to prevent the Environmental Protection Agency under Obama from issuing greenhouse gas regulations that the company says could increase its costs and affect the market for coal and natural gas.

Consol spent more than $3 million on energy and environmental lobbying last year, including the hiring of a Washington firm, Forscey & Stinson, to support legislation that would prohibit the EPA from issuing the greenhouse gas rules.

Romney once expressed clear concerns about global warming. Last June, he told a New Hampshire town hall that humans have contributed to climate change, although it is not clear by how much. "And so I think it's important for us to reduce our emissions of pollutants and greenhouse gases that may well be significant contributors to the climate change and global warming that you're seeing," he said.

On Oct. 27, after Consol gave $150,000 to help Romney's presidential campaign, he visited the Consol Energy Center in Pittsburgh, the arena where the National Hockey League's Penguins play. "My view is that we don't know what's causing climate change on this planet," Romney said. "And the idea of spending trillions and trillions of dollars to try to reduce (carbon dioxide) emissions is not the right course for us."

Six days after Romney's remarks, his campaign deposited $1,000 checks from four of Consol's senior executives." Another executive, J. Brett Harvey, the company's chief executive officer, also serves on Romney's 2012 Pennsylvania Finance Committee.

Consul spokeswoman Lynn Seay said it is common practice for the company "to support political candidates that share a similar philosophy as it relates to a domestic energy policy that recognizes the value and importance of coal and natural gas."

Last month, the EPA objected to Consol's proposal for a mountaintop removal mine in southern West Virginia that would be one of Appalachia's biggest. The EPA had first objected to a permit for the mine on the day that Obama was inaugurated.

Among the pro-Obama group's biggest donors, the Service Employees International Union, has given $1 million so far toward his re-election as it fights Republican plans to restrict the National Labor Relations Board's authority to force employers to move or close plants in efforts to avoid unionization.

The Obama super PAC, Priorities USA Action, also received $100,000 from Law, the managing director of Warland Investments, a commercial real estate and investment firm in Santa Monica, Calif. Law is on the board at Cedars-Sinai and was previously the hospital's chairman. The hospital spent $369,000 in 2011 lobbying on federal health policies during Obama's presidency, according to Senate records.

The pro-Gingrich group, Winning Our Future, has been kept running largely with money from casino mogul Adelson. He and his wife, Miriam, gave $5 million each this month. Miriam's eldest daughter gave $500,000, and her other daughter and son-in-law donated $250,000 each.

Adelson's casino, Las Vegas Sands Corp., has been the target of federal investigations, in part over allegations that the company bribed officials in expanding its Chinese business. A spokesman declined to publicly discuss his boss' support for Gingrich. Adelson wrote last month in an email to The Washington Post: "My motivation for helping Newt is simple and should not be mistaken for anything other than the fact that my wife, Miriam, and I hold our friendship with him very dear and are doing what we can as private citizens to support his candidacy."

The head of a New York-based hedge fund, Singer of Renaissance Technologies, gave the Romney super PAC $1 million. Renaissance lobbied Congress last year on proposals that would aid hedge funds in efforts to collect on debts purchased from Argentina and other foreign governments. Renaissance is one of several international hedge funds that have bought debt in distressed and Third World nations at low prices and sometimes have used lawsuits to force the countries to pay restitution.

A spokesman, Peter Truell, declined to discuss Singer's support for Romney but Renaissance officials have said that buying sovereign debt is only one aspect of the company's business.

Singer has also been outspoken in his criticism of some aspects of the massive overhaul of banking and trading regulations brought by the Dodd-Frank Act and other legislation since the recession. Last August, Romney told a New Hampshire audience that he favored repealing the Dodd-Frank law.

Another executive, William Koch, also gave $1 million to the Romney super PAC from his personal funds and corporate accounts. Koch runs Oxbow Carbon LLC, a fossil fuels processor and mining company that wants changes to laws and regulations on mining, safety issues and climate change. Unlike his brothers, Charles and David Koch, who are long-time supporters of conservative causes, Bill Koch has funded both GOP and Democratic candidates in the past.

"Despite the political statements, this administration has done nothing to help the coal industry, and we feel their energy policy is debatable," said Brad Goldstein, an Oxbow spokesman.

Oxbow also pushed for approval of the Central Rockies Land Exchange, a proposed swap of land tracts in Colorado and Utah to enlarge Koch's 4,500-acre Bear Ranch. The proposed deal with the federal government would allow Koch to acquire several adjacent parcels of federal land in exchange for turning other tracts over to the U.S. The proposal, which requires congressional approval, has brought some local opposition but is under consideration.

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AP Business Writer Daniel Wagner contributed to this report.

Contact the Washington investigative team at DCinvestigations (at) ap.org

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