CHARLOTTESVILLE -- An outdoor political rally erupted into a moment of chaos as protesters drowned out President Obama's speech at a downtown amphitheater here -- and then the rest of the crowd drowned out the protesters.

It was unclear what the protesters were saying, but several members of the crowd said a few minutes later that they heard "Get out of Afghanistan!" The shouts prompted a flurry of Secret Service activity, and they also prompted an enthusiastic crowd of more than 7,000 to shut down the protesters with two cacophonous chants: "Four more years!" and "O-ba-ma!"

Obama couldn't continue for a long moment, but when the noise finally died down, he said: "I couldn't hear what those young people had to say, but that's good that they got involved." To the rest of the crowd, he said: "Don't just chant! Vote!"