First off, polls about the general election taken right now are going to be wrong. Period.
Second, Hillary has put classified material on an unsecured server as an officer sworn to protect and defend the constitution. This should deny her any future office.
Third, Hillary and Bill have used the foundation for payoffs for actions she has taken while in office. She should be in jail for this.
Fourth, Hillary thinks she can be commander in chief when she failed to set proper defenses for our consulate in Libya and then failed to send any aid when the consulate was under attack. For this she should be understood to be incompetent and unpatriotic.
This is a small list of why Hillary is defeat able.
Now, as to why Trump will take her down,
First Trump is a street fighter and does not care if the opponent is a man or woman. She will be savaged for the above actions as she deserves.
Second, Trump will draw from her supporters, because for 8 years Obama has not done anything to improve the middle class job market except for Government workers. The middle class (think blue collar) worker needs jobs to grow in America and this is one of Trump’s main objectives.
Third, Trump is fair, people who work for him are happy to do so. This man has a record of getting things done and so the various groupings of Americans that the left likes to identify will find that they can support Trump easily because the left knows that America is not “whole” under this administration, and Hillary has no ideas except to follow the Obama plan.