Pollsters have credibility?
Vin Gupta, the man you describe as a “pollster” has never conducted a poll in his life. He is a brilliant entrapaneur who’s company infoUSA (publicaly traded) is the pioneer adn leader in the marketing and mailing list business. At the end of 2006, infoUSA acquired the stock of Opinion Research Corporation, one of the world’s leading polling and survey research firms. The CNN polls are national probability samples and the samples are drawn by computer and the CNN editors and polling experts edit all the questions just like any client of a polling company. Mr Gupta, an enthusiastic supporter of Senator Clinton, has nothing to do operationally with the polling operation of Opinion Research. The first time he knows the results is when he watches CNN like the rest of us.
Besides, it is almost impossible to rig a poll. The random probability sample of which households to call is done by computer, the people who actually do the calling follow the script designed by the ORC Scientists and the CNN polling experts. As each individual answer is made, it is entered into the computer, and the polling statisticians and CNN experts view the data in real time. Further, similar questions are asked by other polls and if any poll was way off it would be revealed by its competitors.
There are potentially many things to worry about in the entire relationship between donors, influence, and public positions like ownership of media and the like, but this particular problem is not one of them.