Read this. In short, the legal surveillance, using warrants, was used successfully to stop the terrorists. Not one liberal objects to legal monitoring, getting warrants from the FISA court as required by law. And it was that legal monitoring that caught the latest bunch of scumbags. Don't let anyone tell you otherwise.
We can catch terrorists legally, using the laws in place. Illegally eavesdropping on American citizens without warrants is not needed... and since it's already illegal, the people doing it should be punished as well.