Can you define what you mean by "the public". If you mean the "public" as in a voting entity come about due to universal or male suffrage then it would be 1880s and onwards as detailed in Robert Paxton's "The Anatomy of Fascism".

Basically the public or masses was a term coined to define the people that could now participate in elections, people that unlike before with a more select pool of participants were not as well educated and had no real formal training.

Conservatives had no real way to appeal to them since they had no idea what to do, while more radical groups such as the socialists were very appealing due to their inclusionary wording and policy. Fascists, the most notable of which was the Nazi party also used various techniques to try to get the public to side with them (to varying degrees of success)