A Democratic public relations consultant is suing a Republican blogger for defamation in a case that AP says could offer a key test of the First Amendment rights of bloggers.

AP reports that the lawsuit pits Blois Olson, the president of PR firm New School Communications and a well-known Democratic political commentator, against Michael Brodkorb, a Republican operative who publishes the blog “Minnesota Democrats Exposed.”

In the suit, Olson disputes a series of postings made by Brodkorb last week about criticisms Olson made of the congressional campaign of Democrat Coleen Rowley. Brodkorb wrote that an anonymous source told him that the Rowley campaign refused to hire New School Communications for consulting work, prompting Brodkorb to ask why Olson didn’t disclose that when he criticized Rowley in several news stories.