Pinback button promoting Harry Truman for president, 1948.
Harry Truman had the advantage, or disadvantage, of having served as president for nearly four years before actually running for the office. Rising to the presidency upon the death of Franklin Roosevelt in April 1945, he served out the remainder of his predecessor's term. Running as the incumbent in 1948, he narrowly defeated the same Republican who had challenged FDR in 1944, Thomas Dewey.
Even Truman's supporters thought a victory in the 1948 election was a long shot, if not a lost cause. Thus, slender resources were allocated to producing material for his campaign. Pinbacks, especially those featuring his likeness, are especially scarce and sought-after today, with most examples trading for upwards of $100. If you are looking for a representative example of a genuine 1948 Truman button, but have a limited amount you can spend, this would be an excellent choice.