IBD: yes they claim to be the most accurate. But they can play with their numbers.
In 2008, IBD was showing McCain much better than the average of polls. Right before the election (the last 3 days), IBD’s poll had a huge jump for Obama. They jumped all the way up near the average of polls. That is how they became “accurate” that year.
Officially, they allocated all the “undecided” voters, mostly to Obama.
source: http://www.pollster.com/blogs/hitting_a_bullet_with_a_bullet.html
look at the graph how IBD jumped up in 3 days. I call that manipulation so they could reach the “average”.
It’s shenanigans like this that lead me to hesitate trusting any of the polls, including the ones favorable to Trump.