Public opinion is that body of beliefs held by the people. It is weighted by numbers of adherents to a viewpoint; so, for instance, if 80% of the public favor an initiative, one would say that public opinion is more overwhelmingly on that initiative's side than if only 60% supported it. Public opinion can also be measured in terms of how strongly people support or oppose something; so, for example, if most people are willing to go to such lengths as to vote for a candidate merely on the basis of a single issue, even if he holds unpalatable opinions on other matters, one might say that public opinion is strongly in favor of that stance.
Ludwig von Mises writes, "Wherever and whenever men meet for discussing any affairs of their municipality, state, or nation, public opinion is in the process of evolving and changing, however trifling the immediate topic concerned may be. Public opinion is influenced by anything that is spoken or done in transactions between buyers and sellers, between employers and employees, between creditors and debtors. Public opinion is shaped in the debates of countless representative bodies, committees and commissions, associations and clubs, by editorials and letters to the editor, by the pleading of lawyers and by the opinions of judges."
- Mises, Ludwig von. "The Plain Citizen versus the Professional Propagandist of Bureaucratization". Bureaucracy. http://mises.org/etexts/mises/bureaucracy/section7.asp.