When did it become de rigueur for presidential candidates to play up their humble origins?
In the 1820s. The first six American presidents didn't have to sell themselves as men of the people, because only propertied white men could vote. Expansion of the franchise led to the 1828 election of backwoodsman Andrew Jackson and a shift in presidential image-craft. Candidates suddenly had to appeal to the poor and uneducated masses.
William Henry Harrison, for example, ran the "log cabin and hard cider" campaign of 1840. Abraham Lincoln's near-deification after his 1865 assassination cemented the ideal of the log-cabin president. The Lincoln log cabin became so sacred that a replica stands inside a Greek-style temple on the 16th president's birth site.
Presidential candidates campaigned on their humble origins to varying degrees over the next century or so, depending on the national zeitgeist and whether it was a potent political weapon against a more fortunate opponent. Dwight Eisenhower sold himself as the man from a "small frame house in Abilene, Kansas" to emphasize Adlai Stevenson's relatively privileged background.
But Jimmy Carter barely mentioned his peanut-farm childhood in his acceptance speech at the 1976 Democratic National Convention, possibly because his humble roots had been used against him in the past. When he ran for Georgia governor in 1970, the Atlanta Constitution called him an "ignorant, racist, backward, ultra-conservative, red-necked South Georgia peanut farmer." (Carter did, however, emphasize his rural upbringing in a biographical video.)
In 1980, Ronald Reagan rarely spoke of his alcoholic father and largely uneducated mother.
Although log cabins and humble beginnings are long-running themes in American politics, the significance of those themes has changed over time. The log cabin was originally 19th-century shorthand for "outside the beltway"; Jackson's campaign was built on the idea of seizing power from the Virginians and New Englanders who had dominated the presidency.
By the latter part of the 19th century, however, the log cabin symbolized America's new xenophobia. The Know-Nothing party and its allies warned Americans that immigrants were taking over the United States. When a candidate emphasized his roots in a log cabin on the prairie, he was drawing a contrast to the Catholic immigrants streaming into Eastern cities.
In modern campaigns, humble origins are used almost exclusively to prove to voters that the candidate understands the problems of ordinary people. More than anyone else, Bill Clinton is responsible for this trend. In his autobiographical 1992 convention speech, Clinton described his widowed mother tearfully putting him on a train as a 3-year-old to move in with his grandmother. He also mentioned his grandfather, who ran a country store in Hope, Ark.
The speech showed succeeding candidates how to weave personal struggle and tragedy to policy positions in a way that few candidates had before.
Brian Palmer writes for Slate.