Much of Barack Obama's political success can be traced to a database listing contact information for millions of people, a tool that has proved invaluable in raising record sums of money and organizing a national volunteer network. Now Obama's presidential campaign is increasingly using the list to beat back media messages it does not like, calling on supporters to flood radio and television stations when those opposed to him run anti-Obama ads or appear on talk shows. It did so as recently as Monday night, when it orchestrated a massive stream of complaints on the phone lines of Tribune Co.-owned...