Rasmussen has Dems. tied as Gallup says Hil is up by 11%. Why the big difference?

[comfycouch]

Can anyone point out to me what is the methodology difference between two polls, which were apparently taken at a similar time, yet found very different results?

http://rasmussenreports.com/public_content/politics/election_20082/daily_presidential_tracking_polling_history

[goldcanyonaz]

1. 2008 Pollster Report Card.

[NJSecularist]

2. As I have said, national polls don't mean much anymore

We just had a national primary two days ago. We won't have another one.

Look for state by state polls.

[Kurt_and_Hunter]

3. 3-day vs. 4-day rolling average, live calls vs. robocalls, normal variance

[mrreowwr_kittty]

4. Sample size and weighting, plus participation

Some polls don't include an adequate cross-section of the demographics who will be voting. And a lot of people refuse to do telephone surveys. I do them because I'm a political junkie and I want my opinion to be registered but I often wonder about some of the other people who answer. I speak from my experience doing sales on the phone. There would always be a few eccentric people who just wanted to talk to someone. If you call 10000 people in the hopes of getting 1000 to talk to you (and that's a generous estimate) you are bound to run into some kooks who will throw your sample off.