The polls are reasonably accurate within the margin of error. So Giuliani may not be leading McCain by 20 pts. but only by 15 and Hunter may not have 1% but may have 2.
Polls last Nov had the Republican losing big time and they did.
Can polls be manipulated? Sure. Are they sometimes totally unrepresentative? Absolutely. Just look at the FR polls showing Hunter has a big lead. You don't really believe that do you? You don't really believe Rudy is not leading either do you? You would just dispute the lead.
What about every single poll saying Bush had absolutely no chance whatsoever of winning his second term? Were those polls accurate?