Ratcheting up her offensive against the news media, Gov. Sarah Palin’s attorney threatened Saturday to sue mainstream news organizations if they publish “defamatory” stories relating to whether Palin is under federal investigation. In an extraordinary four-page letter, Alaska-based attorney Thomas Van Flein warns of severe consequences should speculation that until now has largely been confined to blogs about whether Palin embezzled funds in the construction of a Wasilla, Alaska, sports arena find its way into print. “This is to provide notice to Ms. Moore, and those who re-publish the defamation, such as Huffington Post, MSNBC, the New York Times and...