The AAPOR has a good discussion of this.
A so-called “push poll” is an insidious form of negative campaigning, disguised as a political poll. “Push polls” are not surveys at all, but rather unethical political telemarketing — telephone calls disguised as research that aim to persuade large numbers of voters and affect election outcomes, rather than measure opinions. This misuse of the survey method exploits the trust people have in research organizations and violates the AAPOR Code of Professional Ethics and Practices.
The main thing to note is that a ‘push poll’, despite its name, is not actually a poll at all. It is a form of campaigning under the guise of being a poll. Essentially, push polling is conducting very short telephone calls to a very large number of people, specifically to influence their view. For it to be effective you’d need to call a much larger number of people than is typically called for a random political poll.
The fact that a poll contains negative information about one or more candidates does NOT in and of itself make it a ‘push poll.’ Political campaigns routinely sponsor legitimate “message-testing” surveys that are used by campaign consultants to test out the effectiveness of various possible campaign messages or campaign ad content, often including negative messages. Political message-testing surveys may sometimes be confused with fake polling, but they are very different.
If it’s a random survey by an established company, and/or the results are made public, it’s probably not a push poll.