Have you visited the Angus Reid Forum? How does sampling the people that join their forum equate to being truly representative of the general public? Could their 70% opinion poll be replicated in a true random sampling of the general population? 

Did you know that there are benefits to participate in the Angus Reid polls? Check out the FAQ:
https://www.angusreidforum.com/Portal/faqs.aspx#heading3-1

People are giving up home phones to use mobiles and/or IM only - it effects the sampling method that used random phone calls. Which group is likely to hold onto a home phone number? Older Canadians?  

Here's a good read about the shortfalls of polling:

https://www.thestar.com/news/canada/2011/02/14/election_polls_are_fun_but_they_dont_mean_a_thing_pollsters.html