There are many problems with Opinion Polls. No matter how "sciencey" they seem, outcomes can be affected by a great many factors, including, but not limited to:
• how many participants
• how participants are chosen
• how the poll was conducted (telephone, online, in person focus group, self selecting online panel)
• what questions
• the way they are asked
• when they are asked
• opinion poll's intended purpose
• pollster bias
• who paid for the opinion poll.