The Obama administration is the most forceful, vigilant and merciless in cracking down on whistle-blowers and leakers in nearly a century. The liberal law professor in the White House is no softie when it comes to punishing voices who undercut his pronouncements and policies. Since 1917, when the Espionage Act was passed to safeguard national secrets, prior presidents have brought three cases. Since taking office, Obama has used the law six times. In most of these cases, the White House went after whistle-blowers and leakers whose claims embarrassed the Obama administration. Examples of such prosecutions include the massive WikiLeaks disclosure of some 250,000 diplomatic cables along with lesser-known instances such as information about rough interrogations and botched computer operations. The common thread: The White House looked bad. Similar prosecution could happen again with the drone and cyber-war stories, but don't count on it. In these two cases, the results enhanced Obama's image, a result that won't draw presidential ire. Also, the news accounts that showed the president in charge of drone targets and approving a computer-jamming worm didn't disclose direct intelligence details or names. But there's a disturbing pattern, especially as the November election draws closer. This White House is bothered by the ever-present suggestion that it's weak on terrorism or hesitant to look tough against looming enemies - and it's willing to go to extraordinary means to pursue leaks of unflattering stories.