1
general::
Appeal to spectators for maximum approval, as in He peppers his speeches with humor and wisecracks about his opponent, clearly playing to the gallery. In this term gallery refers to the cheapest seats in a British theater and hence the least sophisticated audience. [Late 1800s]
American Heritage Idioms
2
general::
Phrase(s): play to the gallery [and] play to the crowd
to perform in a manner that will get the strong approval of the audience; to perform in a manner that will get the approval of the lower elements in the audience. • John is a competent actor, but he has a tendency to play to the crowd. • When he made the rude remark, he was just playing to the gallery.
McGrawhill's American Idioms And Phrasal Verbs