Answer:
to convince the audience to take an action.
Step-by-step explanation:
The primary purpose of this poster is to convince the audience to take an action, in very particular terms, it intends to motivate people to, first of all, register to vote, and, secondly, to vote for the Democratic Party, its representatives, and the very basic principles that they specifically spouse in this poster, which are lasting peace and security for all, principles that one can assume are not those of the competing party, in this case, the Republican Party.