Interestingly, the tendency is to believe polls that favor your candidates and discredit those that show them to be behind. Strategically however, the opposite works much better. Assume you’re behind if the polls tell you so. Assume you’re not doing as well if they tell you you’re winning.
This year, mistrusting polls has another more ominous implications for Trump followers, this misguided assumption that if he loses, he was cheated. While it helps that you are pointing out this is wrong, the candidate himself will have to tell his followers that it’s just not true.