According to tax records unearthed by Bloomberg News, the health insurance lobby secretly gave $86.2 million to the U.S. Chamber of Commerce in 2009 to try to prevent the health care bill from becoming law. The huge contribution  40 percent of the chamber’s spending for that year  allowed the group to run ads against the bill without tainting the insurance industry, which was negotiating with Democrats on the bill at the same time.

This year, the chamber raised nearly $33 million in secret donations for political ads in the midterm elections, almost all of which was used to elect Republicans who have vowed to repeal the health care law. Did some of that money come, once again, from health insurance companies that were unwilling to attach their names to their contributions? It’s a logical assumption, but only the donors and the chamber know for sure.

And that’s the problem with secret political donations, which played such a large role in the elections earlier this month. They cast a shadow of doubt and distrust over a huge field, raising questions about who is covertly pushing which bill and supporting which candidate, and for which self-serving purposes. Lobbying and political contributions can be perfectly legitimate practices, but only when the public can see who is pulling the strings.

Secret donors spent at least $138 million on the midterm elections, according to the latest figures, and 80 percent of that secret money supported Republican candidates. What will those donors get for their money, and who will they get it from?