When it comes to presidential elections, all politics is dirty. As Susan Estrich, Michael Dukakis's campaign manager in 1988, says, "He who doesn't throw mud ends up covered in it." The 2008 election has been no exception to the truth that Dukakis learned the hard way, and the electorate can look forward to almost six more months of mud blizzards before Election Day clears the campaign skies in November.

In this third report from the Center for Public Integrity's The Buying of the President series, Stephanie Mencimer examines dirty tricks in politics, like the recent rumors that Barack Obama is a practicing Muslim. Who are the opposition researchers or tricksters who dig up this dirt? Her investigation attempts to answer these questions and more.