The argument against this is that the experts, the people who are paid to work for the campaign, spend a lot of money on polls. Now it could be they aren't real experts, just scam artists, "beltway bandits" but arguments against polls should explain this

They’re using polls for something different than we are - they want to know where they can mine for votes & where their support is weak or strong so they know where to focus their efforts, not what the outcome will be. Polls can help them with targeting, they can’t predict the outcome.