On October 5, 1947, Harry Truman sat at a desk in the White House and asked the country to stop eating meat on Tuesdays and poultry on Thursdays, so that the grain it would have fed could be shipped to Europe. It was the first presidential address carried on television. There were about 44,000 sets in the United States, nearly all of them in the north-east and many of them in bars, and estimates of who saw it range from tens of thousands to a few hundred thousand.
The emergency was real. The winter of 1946 and 1947 had been the worst in Europe in living memory, the German harvest had failed, and the American grain shipments keeping people alive were running into a Congress that wanted to cut them. Truman had appointed a Citizens Food Committee under Charles Luckman in the summer, and the committee had asked for voluntary rationing rather than controls.
He had already given the more consequential speech six months earlier. On March 12 he asked Congress for 400 million dollars for Greece and Turkey and set out what became known as the Truman Doctrine, that it must be the policy of the United States to support free peoples resisting subjugation. This one asked people to eat less. It did not work. Consumption went up.
The medium was the interesting part. Roosevelt had used radio fireside chats to extraordinary effect and had appeared on television at the 1939 World's Fair, but not in a way anybody watched. Truman's 1947 address was a formal speech delivered to a camera, and the conventions it set, the desk, the direct address, the short sentences, are the ones still in use.
What changed American political television was 1960, when the Kennedy Nixon debates were watched by about 70 million people and the visual impression decided a large number of votes. By then there were about 45 million sets. The audience was small in 1947, and this speech is remembered for being first rather than for anything it achieved.