As pollsters for two Democratic presidents who served before Barack Obama, we view this unprecedented attempt to silence the media and to attack the credibility of unpopular polling as chilling to the free exercise of democracy.

This is more than just inside baseball. As practicing political consultants, both of us have seen that the established parties try to stifle dissent among their political advisers and consultants. The parties go out of their way to try to determine in advance what questions will be asked and what answers will be obtained to reinforce existing party messages. The thing most feared is independence, which is what Mr. Rasmussen brings.

Mr. Gibbs’s comments and the recent attempts by the Democratic left to muzzle Scott Rasmussen reflect a disturbing trend in our politics: a tendency to try to stifle legitimate feedback about political concerns—particularly if the feedback is negative to the incumbent administration.