Washington ? 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 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 Gingrich’s political committee, has acknowledged it’s under federal criminal investigation by the Securities and Exchange Commission and the Justice Department 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 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.

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.