How can anyone form an opinion on the contents of something they haven't read? The answer, as James pointed out, is that they form their opinion on the spot based on something less that complete exposure to the bill, and something more than what is actually in it.

Having work in the field service industry (the part that actually conducts the survey) I understand how much of an impact the interviewer can have on which way those spontaneous opinions are formed. If you don't have a strong opinion, you might be less willing to tell someone with an Hispanic accent that you oppose immigration. Emphasis can also have an impact, if they put a stronger emphasis on "illegal" they will form a different opinion than if they put an emphasis on "immigration". Some firms are turning to pre-recorded audio to ask the questions, so they know that every respondent gets ask the same way. Even then, you never know if your particular combination of questions and wording will influence the opinion of the respondent.

I do know I have absolutely no basis for trusting the federal government to close the borders down. In this I have the facts on my side. I am old enought that I was very opposed to the 1986 amnesty bill. I was right and all those who accused me back the were either disingenuous or more uninformed than I was.

Don't feed me comprehensive (amnesty) reform; IT's THE BORDERS STUPID!