Some donors volunteered their names at the time of their gifts or when asked by reporters. What little is known about the others suggests that a good number are as interested in influencing public policy, or benefiting from the Clintons' worldwide ties, as they are in supporting presidential scholarship or economic development.

The Saudi royal family gave $10 million, according to The Washington Post, and numerous foreign governments have given $1 million. The largest contributors appear to include Mexican billionaire Carlos Slim Helú, Canadian mining entrepreneur Frank Giustra and the Lundin Group, a Canadian oil and gas company. Each has publicly pledged $100 million for development projects.

These gifts raise a number of questions, particularly in the case of Giustra, who in 2005 flew with Clinton to Kazakhstan, where his connections to the former president impressed officials enough to win him a lucrative uranium mining contract. They also raise the question of what favors might be sought by other donors who don't want to be identified.

Clinton argues that the confidentiality he promised his donors should take precedence over calls for transparency, and that he should not be judged by a different standard from other former presidents who have been allowed to keep their library donors secret.

Some philanthropic organizations go even further. Paulette Maehara, president of the Association of Fundraising Professionals, says that "if donors cannot trust charities to respect their wishes, then philanthropy simply cannot happen."

These arguments would be valid in most contexts. But given Clinton's unusual circumstances, gifts to his foundation could rightly be seen as a back door into the good graces of someone who could be a key adviser to the next president. The stakes are simply too high not to have principles of open government take precedence over common fundraising practices.