Even the Republican National Committee is fending off a concerted effort to keep the party's money from candidates that don't pass a "purity" test.

CNN: Democrats need to learn to compromise

Law enforcement agents should be able to test the toxin found in the letters to determine its potency and purity, as well as learn what chemicals may have been used to extract it from widely available castor beans, said Murray Cohen, the founder of the Atlanta-based Frontline Foundation, which trains workers on preparedness and response to bioterrorism and epidemics.

NPR: Experts: Ricin Like That In Letters Easy To Make