If you flip a thousand pennies and flip each one 10 times, a few will land heads up every time.
If you take one of those heads-only pennies and flip it an 11th time, the odds of it landing heads up is 50%, just like every other penny in the world.
Polls are no different than pennies.
Except that, in this case the particular poll, the penny always landed right side up - for the past 100 years.