Surveys taken on the weekends tend to under reported conservatives and Republicans. I have no idea why but when I worked @ the Public Policy Research Institute @ Texas A&M University (try saying that 200 times a day), we did several political surveys and we were always told the same thing on the first night the survey went into "production". You'll get more Democrats and liberals on the weekends and more conservatives and Republicans during the week, usually on the evening shifts.
That was a interesting job, getting told to F*** off 5-10 times a days really made one feel good. I'm glad I don't work there anymore. It was a stressful time and telling that one supervisor to pull his head out of his as* was a great way to make an exit.