Money pouring into the presidential election from super political action committees and nonprofit campaign groups appears so far to be strictly American in origin, donated by U.S. companies, unions and millionaires. But it's easier than ever to conceal the source of money and the identities of contributors, making conditions ripe for illegal donations from foreigners, overseas companies or governments attempting to help a favored candidate for the White House.

"Clearly it is more difficult to enforce the ban on foreign spending when the source of the money is not publicly disclosed," said Trevor Potter, head of the Campaign Legal Center and former chairman of the Federal Elections Commission. Potter is the attorney advising television comedian Stephen Colbert, who set up his own super PAC to illustrate absurdities of how money affects U.S. elections.

Foreign political donations have been outlawed since 1966, and a brief U.S. Supreme Court order last month upheld the ban for foreigners living in the U.S. as well as corporations and individuals abroad.