Truman--the donkey is the symbol for the Democratic Party and Truman was the presidential candidate for the 1948 election.
There are a few cartoons with Truman riding a donkey for this election. Truman was Franklin Roosevelt's vice president and takes over after FDR dies in 1945. This is Truman's first and only election with him running as president. He won the election against Thomas Dewey. Dewey was proclaimed the winner before the official count was over and in the end Truman won the election.
